Systems and Methods for Harmonic Resonance Control

ABSTRACT

Systems and methods for harmonic resonance control are described. In some embodiments, a system comprises a first switch-controlled VAR source and a harmonic management block which may each be configured to be coupled to a distribution power network. The first switch-controlled VAR source may comprise a first processor, a voltage compensation component, and a switch. The first processor may be configured to enable the voltage compensation component after a delay by controlling the switch based on first proximate voltage after a duration associated with the delay to adjust voltage volt-ampere reactive. The harmonic management block may be configured to compare a second proximate voltage to at least one resonant threshold to detect potential resonance caused by enablement of the voltage compensation component and to engage based on the comparison the resonance compensation component to manage the potential resonance.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of and claims thebenefit of U.S. Nonprovisional patent application Ser. No. 13/488,330,filed Jun. 4, 2012, entitled “Systems and Methods for Edge of NetworkVoltage Control of a Power Grid,” which claims priority to U.S.Provisional Patent Application No. 61/535,892, filed Sep. 16, 2011,entitled “Systems and Methods of a Distributed Dynamic VAR (D-DVAR)Compensator,” U.S. Provisional Patent Application No. 61/567,580, filedDec. 6, 2011, entitled “Systems and Methods for Dynamic VAROptimization,” U.S. Provisional Patent Application No. 61/579,610, filedDec. 22, 2011, entitled “Systems and Methods for Managing Power,” U.S.Provisional Patent Application No. 61/635,799, filed Apr. 19, 2012,entitled “Systems and Methods for Dynamic AC Line Voltage Regulationwith Energy Saving Tracking,” and U.S. Provisional Patent ApplicationNo. 61/635,797, filed Apr. 19, 2012, entitled “Systems and Methods forFast VAR Source with Anti-Resonance Function,” all of which areincorporated by reference herein. This application is also acontinuation-in-part of and claims the benefit of pending U.S.Nonprovisional patent application Ser. No. 13/707,560, filed Dec. 6,2012, entitled “Systems and Methods for Switch-Controlled VAR SourcesCoupled to a Power Grid,” which is a continuation-in-part of and claimsthe benefit of U.S. Nonprovisional patent application Ser. No.13/488,330, filed Jun. 4, 2012, entitled “Systems and Methods for Edgeof Network Voltage Control of a Power Grid,” which claims priority toU.S. Provisional Patent Application No. 61/535,892, filed Sep. 16, 2011,entitled “Systems and Methods of a Distributed Dynamic VAR (D-DVAR)Compensator,” U.S. Provisional Patent Application No. 61/567,580, filedDec. 6, 2011, entitled “Systems and Methods for Dynamic VAROptimization,” U.S. Provisional Patent Application No. 61/579,610, filedDec. 22, 2011, entitled “Systems and Methods for Managing Power,” U.S.Provisional Patent Application No. 61/635,799, filed Apr. 19, 2012,entitled “Systems and Methods for Dynamic AC Line Voltage Regulationwith Energy Saving Tracking,” and U.S. Provisional Patent ApplicationNo. 61/635,797, filed Apr. 19, 2012, entitled “Systems and Methods forFast VAR Source with Anti-Resonance Function,” all of which areincorporated by reference herein.

BACKGROUND

1. Field of the Invention(s)

The present invention(s) generally relate to power distribution gridnetwork optimization strategies. More particularly, the invention(s)relate to systems and methods for harmonic resonance control.

2. Description of Related Art

The conventional approach to power distribution grid voltage control isbased on techniques developed about 70 years ago. In recent years,highly complex and expensive systems have been required to implementimproved effective voltage control and conservation voltage reduction(CVR) based demand reduction. Under present requirements, alternatingcurrent (AC) line voltage for connected users needs to fall within anarrow band specified by ANSI C84.1 under all conditions of loading andsubstation voltage. Typically, utilities operate in a narrow band of116-124 volts, even though level ‘A’ service allows for a range of114-126 volts. The difficulty in adhering to a tight regulation bandarises from normal fluctuations in incoming line voltage at thesubstation, as well as load changes along the feeder. These changescause the line voltage to vary, with utilities required to maintainvoltage for consumers within specified bounds.

The prior art volt-ampere reactive regulation devices (VAR devices) forvoltage control may be split into several categories including: 1) priorart VAR devices with slow responding capacitors and electro-mechanicalswitches; ii) prior art VAR devices with medium response capacitors andthyristor switched capacitors; and iii) prior art VAR devices with powerconverter based VAR control using Static VAR sources or staticsynchronous condensers (STATCOMs).

It should be noted that capacitors in the prior art VAR devices aremainly used for power factor control when used by customers and forvoltage control when used by utilities. For power factor control, thedownstream line current must be measured. Capacitors and/or inductorsmay be switched on or off based on the line current to realize a desiredoverall power factor (e.g., typically at a value of unity). In thesecond case of voltage control used by utilities, capacitors arecontrolled based on: 1) local voltage measurements; 2) other parameterssuch as temperature; 3) line reactive current; and/or 4) dispatchescommunicatively received from a control center. The control center maydispatch decisions regarding capacitor control based on informationreceived from multiple points in the network.

Most capacitors of prior art VAR devices are switched usingelectromechanical switches. The electromechanical switches are limitedin switching speed and by life of the switches. Many electromechanicalswitches are limited to 3-4 switches per day. A response time ofapproximately fifteen minutes is often required to enable voltagecontrol with prior art VAR devices. During this time, the followingsteps may be performed: 1) sensing voltages locally; 2) communicatingthe sensed voltages to a centralized control center; 3) power and/orvoltage modeling of the system at the centralized control center; 4)determining to take action based on the model and perceived potentialimprovements; and 5) dispatching one or more commands from thecentralized control center to the prior art VAR device to switch thecapacitor. More advanced Volt-VAR Optimization or VVO systems are movingto such centralized implementations so they can try to optimize theprofile of voltage along an entire distribution feeder and reduceinfighting between prior art VAR devices.

SUMMARY

Systems and methods for an edge of network voltage control of a powergrid are described. In some embodiments, a system comprises adistribution power network, a plurality of loads, and a plurality ofshunt-connected, switch-controlled VAR sources. The loads may be at ornear an edge of the distribution power network. Each of the loads mayreceive power from the distribution power network. The plurality ofshunt-connected, switch-controlled VAR sources may be located at theedge or near the edge of the distribution power network where they mayeach detect a proximate voltage. Further, each of the VAR sources maycomprise a processor and a VAR compensation component. The processor maybe configured to enable the VAR source to determine, after a delay,whether to enable the VAR compensation component based on the proximatevoltage and to adjust network volt-ampere reactive by controlling aswitch to enable the VAR compensation component.

The delay of each of the plurality of shunt-connected, switch-controlledVAR sources may not be equal. The different delays of different membersof the plurality of shunt-connected, switch-controlled VAR sources mayprevent infighting between at least two of the different members. Invarious embodiments, the delay of at least two of the plurality ofshunt-connected, switch-controlled VAR sources may be equal but thedelay of a third of the plurality of shunt-connected, switch-controlledVAR sources may not be equal to the other two VAR sources.

The switch may comprise a semiconductor switch in series with an NTC orresistor. The semiconductor switch (in series with the NTC or resistor)may be in parallel with a relay. The semiconductor switch may becontrolled by a first signal from the processor and the relay may becontrolled by a second signal from the processor. The semiconductorswitch may control enabling the VAR compensation component and relievesthe relay of switching stress. The relay may conduct when thesemiconductor switch is active thereby reducing semiconductor deviceconduction losses.

In various embodiments, at least two of the plurality ofshunt-connected, switch-controlled VAR sources are on a low voltage sideof a transformer of the power distribution network. The VAR compensationcomponent may comprise capacitors or inductors.

In some embodiments, each of the plurality of shunt-connected,switch-controlled VAR sources includes at least one voltage set point.Each of the processors of the plurality of shunt-connected,switch-controlled VAR sources may be configured to determine whether toenable the VAR compensation component based on a comparison of theproximate voltage to the at least one voltage set point. Each of theplurality of shunt-connected, switch-controlled VAR sources may increaseleading volt-ampere reactive if the at least one voltage set point ishigher than the detected proximate voltage and decrease leadingvolt-ampere reactive if the at least one voltage set point is lower thanthe detected proximate voltage.

In some embodiments, each of the plurality of shunt-connected,switch-controlled VAR sources comprises a communication moduleconfigured to receive at least one voltage set point. The communicationmodule of different shunt-connected, switch-controlled VAR sources mayreceive updates for the at least one voltage set point(s). Thecommunication module may be configured to update the voltage set pointand a rate of update of the voltage set point may be significantlyslower than adjusting the network volt-ampere reactive by controllingthe switch to enable the VAR compensation component based on thedetermination. In some embodiments, at least two of the plurality ofshunt-connected, switch-controlled VAR sources receive different voltageset points.

In some embodiments, the processor is further configured to detect anovervoltage condition and disable the switch based on the detectedovervoltage condition. In various embodiments, the systemself-determines which VAR compensation components of the plurality ofVAR sources are enabled and which VAR compensation components of theplurality of VAR sources are not enabled.

An exemplary method comprises detecting, by a first shunt-connected,switch-controlled VAR source at an edge or near the edge of adistribution power network proximate to a first load, a first proximatevoltage, the first load configured whether to receive power from thedistribution power network, the first shunt-connected, switch-controlledVAR source comprising a processor and a VAR compensation component,determining, after a first delay, by the processor of the firstshunt-connected, switch-controlled VAR source, whether to enable the VARcompensation component based on the first proximate voltage, adjusting,by the VAR compensation component of the first shunt-connected,switch-controlled VAR source, a network volt ampere based on thedetermination.

The method may further comprise detecting, by a second shunt-connected,switch-controlled VAR source at the edge or near the edge of thedistribution power network proximate to a second load, a secondproximate voltage, the second shunt-connected, switch-controlled VARsource comprising a VAR compensation component and a processor,determining, after a second delay, by the processor of the secondshunt-connected, switch-controlled VAR source, whether to enable the VARcompensation component based on the second proximate voltage after asecond delay; adjusting, by the VAR compensation component of the secondshunt-connected, switch-controlled VAR source, the network volt amperebased on the determination.

The first delay may not equal to the second delay. The different delaysof different members of the plurality of shunt-connected,switch-controlled VAR sources may prevent infighting between at leasttwo of the different members.

Another exemplary method may comprise coupling a first switch-controlledVAR source in shunt on a distribution power network, the firstswitch-controlled VAR source being proximate to a first load at or nearan edge of the distribution power network, the first load beingconfigured to receive power from the distribution power network, thefirst switch-controlled VAR source configured to detect a firstproximate voltage at the edge or near the edge of the distribution powernetwork, the first switch-controlled VAR source comprising a VARcompensation component and a processor, the processor configured toenable the first switch-controlled VAR source to determine, after afirst delay, whether to enable the VAR compensation component based onthe first proximate voltage and to adjust network volt-ampere reactiveby controlling a switch to enable the VAR compensation component basedon the determination.

The method may further comprise coupling a second switch-controlled VARsource in shunt on a distribution power network, the secondswitch-controlled VAR source being proximate to a second load at or nearan edge of the distribution power network, the second load beingconfigured to receive power from the distribution power network, thesecond switch-controlled VAR source configured to detect a secondproximate voltage at the edge or near the edge of the distribution powernetwork, the second switch-controlled VAR source comprising a VARcompensation component and a processor, the processor configured toenable the second switch-controlled VAR source to determine, after asecond delay, whether to enable the VAR compensation component based onthe second proximate voltage and to adjust network volt-ampere reactiveby controlling a switch to enable the VAR compensation component basedon the determination.

The first delay may not be equal to the second delay. The differentdelays of different members of the plurality of shunt-connected,switch-controlled VAR sources may prevent infighting between at leasttwo of the different members.

In various embodiments, a system comprises a distribution power networkcoupled to the first switch-controlled VAR source. The firstswitch-controlled VAR source may comprise a processor, a voltagecompensation component, and a switch.

The first switch-controlled VAR source may be configured to obtain afirst delay value that is different from another delay value of anotherswitch-controlled VAR source coupled to the distribution power network,monitor a first proximate voltage of the distribution power network, thefirst proximate voltage being proximate to the first switch-controlledVAR source, initiate a first delay duration based on the comparison ofthe first proximate voltage to at least one set point, the first delayduration being based on the first delay value, determine, with theprocessor, after the first delay duration, whether to connect thevoltage compensation component based on the monitored voltage, themonitored voltage being possibly changed by the other switch-controlledVAR source, and control, based on the determination, the switch toconnect the voltage compensation component to adjust a network voltageor a network voltage component associated with the distribution powernetwork.

In some embodiments, the first switch-controlled VAR source configuredto obtain the first delay value comprises the switch-controlled VARsource configured to generate the first delay value. Theswitch-controlled VAR source configured to generate the first delayvalue may comprise the switch-controlled VAR source configured togenerate the first delay value with a randomizer (e.g., random numbergenerator). The first switch-controlled VAR source configured to obtainthe first delay value may comprise the first switch-controlled VARsource receiving, via a communication interface of the switch-controlledVAR source, the first delay value. The first switch-controlled VARsource configured to obtain the first delay value may comprise a memoryof the first switch-controlled VAR source configured to store the firstdelay value, the memory being accessible by the processor.

In some embodiments, the first switch-controlled VAR source configuredto control, based on the determination, the switch to connect thevoltage compensation component to adjust the network voltage or thenetwork voltage component associated with the distribution power networkcomprises the first switch-controlled VAR source configured to control,based on the determination, the switch to connect the voltagecompensation component to adjust real power, reactive power, or bothreal and reactive power.

The system may further comprise a second switch-controlled VAR sourcecoupled to the distribution power network. The second switch-controlledVAR source may be configured to obtain a second delay value that isdifferent from the first delay value, monitor a second proximate voltageof the distribution power network, the second proximate voltage beingproximate to the second switch-controlled VAR source, initiate a seconddelay duration based on the comparison of the second proximate voltageto at least one set point, the second delay duration being based on thesecond delay value, determine, by a processor of the secondswitch-controlled VAR source, after the second delay duration, whetherto connect a voltage compensation component of the secondswitch-controlled VAR source based on the monitored second proximatevoltage, the monitored second proximate voltage being changed by thefirst switch-controlled VAR source before the end of the second delayduration, and control, based on the determination, a switch of thesecond switch-controlled VAR source to connect the voltage compensationcomponent of the second switch-controlled VAR source to adjust a networkvoltage or a network voltage component associated with the distributionpower network.

In various embodiments, the system may further comprise a secondswitch-controlled VAR source coupled to the distribution power network.The second switch-controlled VAR source may be configured to obtain asecond delay value that is different from the first delay value, monitora second proximate voltage of the distribution power network, the secondproximate voltage being proximate to the second switch-controlled VARsource, initiate a second delay duration based on the comparison of thesecond proximate voltage to at least one set point, the second delayduration being based on the second delay value, and determine, by aprocessor of the second switch-controlled VAR source, after the seconddelay duration, to not connect a voltage compensation component of thesecond switch-controlled VAR source based on the monitored secondproximate voltage, the monitored second proximate voltage being changedby the first switch-controlled VAR source before the end of the seconddelay duration.

The first switch-controlled VAR source may be further configured toobtain a different delay value that is longer than the first delay valueafter control of the switch. In some embodiments, the switch comprises asemiconductor switch in series with an NTC or resistor, and wherein thesemiconductor switch in series with the NTC or resistor is in parallelwith a relay.

An exemplary method comprises obtaining, by a first switch-controlledVAR source coupled to a distribution power network, a first delay valuethat is different from another delay value of another switch-controlledVAR source coupled to the distribution power network, monitoring a firstproximate voltage of the distribution power network, the first proximatevoltage being proximate to the first switch-controlled VAR source,initiating a first delay duration based on the comparison of the firstproximate voltage to at least one set point, the first delay durationbeing based on the first delay value, determining, with a processor ofthe first switch-controlled VAR source, after the first delay duration,whether to connect a voltage compensation component of the firstswitch-controlled VAR source based on the monitored voltage, themonitored voltage being possibly changed by the other switch-controlledVAR source, and controlling, based on the determination, a switch of thefirst switch-controlled VAR source to connect the voltage compensationcomponent to adjust a network voltage or a network voltage componentassociated with the distribution power network.

An exemplary computer readable medium may comprise instructionsexecutable by a processor for performing a method. The method maycomprise obtaining, by a first switch-controlled VAR source coupled to adistribution power network, a first delay value that is different fromanother delay value of another switch-controlled VAR source coupled tothe distribution power network, monitoring a first proximate voltage ofthe distribution power network, the first proximate voltage beingproximate to the first switch-controlled VAR source, initiating a firstdelay duration based on the comparison of the first proximate voltage toat least one set point, the first delay duration being based on thefirst delay value, determining, with a processor of the firstswitch-controlled VAR source, after the first delay duration, whether toconnect a voltage compensation component of the first switch-controlledVAR source based on the monitored voltage, the monitored voltage beingpossibly changed by the other switch-controlled VAR source, andcontrolling, based on the determination, a switch of the firstswitch-controlled VAR source to connect the voltage compensationcomponent to adjust a network voltage or a network voltage componentassociated with the distribution power network.

An exemplary system comprises a distribution power network and aplurality of loads at or near an edge of the distribution power network,each of the plurality of loads configured to receive power from thedistribution power network. The system may further comprise a pluralityof shunt-connected, switch-controlled VAR sources at the edge or nearthe edge of the distribution power network which may each be configuredto detect a first proximate voltage at the edge or near the edge of thedistribution power network. Each of the plurality of shunt-connected,switch-controlled VAR sources comprising a first processor and a voltagecompensation component, the processor configured to enable theshunt-connected, switch-controlled VAR source to determine, after adelay, whether to enable the VAR compensation component based on thefirst proximate voltage to adjust voltage volt-ampere reactive bycontrolling the VAR compensation component based on the determination.The exemplary system may further comprise a plurality of harmonicmanagement blocks coupled to the distribution power network. Each of theharmonic management block comprising a resonance detection module and aresonance compensation component, each harmonic management blockconfigured to compare a second proximate voltage to at least oneresonant threshold to detect potential resonance caused by enablement ofthe voltage compensation component of at least one of the plurality ofshunt-connected, switch-controlled VAR sources, and to engage based onthe comparison the resonance compensation component to manage thepotential resonance.

The resonance detection module may comprise an inductor and a zenerdiode. The resonance threshold may be a break down voltage of the zenerdiode. The resonance compensation component may comprise a transistorand a resistor, the transistor closing based on a comparison of voltageacross the inductor to the resonance threshold to engage the resistorand dampen the potential resonance.

In some embodiments, the resonance detection module may comprise atransformer and an inverter. The resonance compensation component maycomprise at least one capacitor and wherein the inverter with the atleast one capacitor is configured to synthesize harmonic voltages inanti-phase to cancel potential resonance.

In various embodiments, the resonance detection module may comprise aninductor and an LED. The resonance compensation component may comprise aprocessor configured to enable or disable the VAR compensation componentof at least one of the shunt-connected, switch-controlled VAR sourcesbased on light from the LED.

Another exemplary system may comprise a distribution power network and aplurality of loads at or near an edge of the distribution power network,each of the plurality of loads configured to receive power from thedistribution power network. The system may further comprise a pluralityof shunt-connected, switch-controlled VAR source at the edge or near theedge of the distribution power network. Each of the plurality ofshunt-connected, switch-controlled VAR sources may be configured todetect a first proximate voltage at the edge or near the edge of thedistribution power network. Each of the plurality of shunt-connected,switch-controlled VAR sources may comprise a first processor and avoltage compensation component, the processor configured to enable theshunt-connected, switch-controlled VAR source to determine, after adelay, whether to enable the VAR compensation component based on thefirst proximate voltage to adjust voltage volt-ampere reactive bycontrolling the VAR compensation component based on the determination.The system may further comprise a plurality of means for managingpotential resonance, the plurality of means coupled to the distributionpower network. Each of the plurality of means may comprise a resonancedetection module and a resonance compensation component. Each of theplurality of means may be configured to compare a second proximatevoltage to at least one resonant threshold to detect potential resonancecaused by enablement of the voltage compensation component of at leastone of the plurality of shunt-connected, switch-controlled VAR sources,and to engage based on the comparison the resonance compensationcomponent to manage the potential resonance.

Another exemplary system comprises a first switch-controlled VAR sourceconfigured to be coupled to a distribution power network. The firstswitch-controlled VAR source may comprise a first processor, a voltagecompensation component, and a switch, the first processor configured toenable the voltage compensation component after a delay by controllingthe switch based on first proximate voltage after a duration associatedwith the delay to adjust voltage volt-ampere reactive. The system mayfurther comprise a harmonic management block configured to be coupled tothe distribution power network, the harmonic management block comprisinga resonance detection module and a resonance compensation component. Theharmonic management block may be configured to compare a secondproximate voltage to at least one resonant threshold to detect potentialresonance caused by enablement of the voltage compensation component andto engage based on the comparison the resonance compensation componentto manage the potential resonance.

The resonance detection module may comprise an inductor and a zenerdiode. The resonance threshold may be a break down voltage of the zenerdiode. The resonance compensation component may comprise a transistorand a resistor, the transistor closing based on a comparison of voltageacross the inductor to the resonance threshold to engage the resistorand dampen the potential resonance.

In some embodiments, the resonance detection module may comprise atransformer and an inverter. The resonance compensation component maycomprise at least one capacitor and wherein the inverter with the atleast one capacitor is configured to synthesize harmonic voltages inanti-phase to cancel potential resonance.

In various embodiments, the resonance detection module may comprise aninductor and an LED. The resonance compensation component may comprise aprocessor configured to enable or disable the VAR compensation componentof at least one of the shunt-connected, switch-controlled VAR sourcesbased on light from the LED.

Another exemplary system comprises a first switch-controlled VAR sourceand a harmonic management block. The first switch-controlled VAR sourcemay be configured to be coupled to a distribution power network. Thefirst switch-controlled VAR source may comprise a first processor, avoltage compensation component, and a switch. The first processor may beconfigured to enable the voltage compensation component after a delay bycontrolling the switch based on first proximate voltage after a durationassociated with the delay to adjust voltage volt-ampere reactive. Theharmonic management block may be configured to be coupled to thedistribution power network. The harmonic management block may comprise ameans for detecting resonance and a means for compensation of resonance.The means for detecting resonance may be configured to compare a secondproximate voltage to at least one resonant threshold to detect potentialresonance caused by enablement of the voltage compensation component andthe means for compensation of resonance may be configured to manage thepotential resonance based on the comparison.

An exemplary method may comprise installing a first switch-controlledVAR source configured to a distribution power network, the firstswitch-controlled VAR source comprising a first processor, a voltagecompensation component, and a switch, the first processor configured toenable the voltage compensation component after a delay by controllingthe switch based on first proximate voltage after a duration associatedwith the delay to adjust voltage volt-ampere reactive and installing aharmonic management block configured to the distribution power network,the harmonic management block comprising a resonance detection moduleand a resonance compensation component, the harmonic management blockconfigured to compare a second proximate voltage to at least oneresonant threshold to detect potential resonance caused by enablement ofthe voltage compensation component and to engage based on the comparisonthe resonance compensation component to manage the potential resonance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a depicts a typical distribution feeder fed from a singlesubstation in some embodiments.

FIG. 1 b depicts a distribution feeder fed from a single substation andincluding a plurality of edge of network voltage optimization (ENVO)devices in some embodiments.

FIG. 1 c depicts another distribution feeder fed from a singlesubstation and including the plurality of ENVO devices in someembodiments.

FIG. 2 is a diagram depicting voltage drop along feeders due to loadswithout the implementation of capacitor banks in the prior art.

FIG. 3 a is a diagram depicting a power distribution grid withshunt-connected, switch-controlled VAR sources at or near each load insome embodiments.

FIG. 3 b is another diagram depicting a power distribution grid withshunt-connected, switch-controlled VAR sources at or near each load insome embodiments.

FIG. 4 a is a circuit diagram of an exemplary switch-controlled VARsource which may be connected in shunt in some embodiments.

FIG. 4 b is a graph that depicts activating the semiconductor switchrelative to the relay to engage VAR compensation in some embodiments.

FIG. 4 c is a graph that depicts deactivating the semiconductor switchrelative to the relay to disengage VAR compensation in some embodiments.

FIGS. 5 a and 5 b are graphs that depict a desired voltage range inrelation to set points in some embodiments.

FIG. 6 is a flow chart for voltage regulation by a switch-controlled VARsource in some embodiments.

FIG. 7 is a time sequence of events of network regulation with twoswitch-controlled VAR sources in some embodiments.

FIG. 8 is a graph that depicts a typical voltage profile at variousnodes in the prior art.

FIG. 9 is a graph that depicts relatively flat voltage profile atvarious nodes in some embodiments realized with 240 switch controlledVAR sources operating to regulate the voltage along the edge of thedistribution feeder.

FIG. 10 is a graph that depicts a dynamic response of the ENVO system toline voltage changes (which can be caused by solar PV plants), as wellas to step changes in line loading in some embodiments.

FIG. 11 a is another circuit diagram of a plurality of switch-controlledVAR sources that may be within or next to a pole top transformer or anygrid asset in some embodiments.

FIG. 11 b depicts a switch-controlled VAR source in some embodiments.

FIG. 11 c depicts a plurality of switch-controlled VAR sources in someembodiments.

FIG. 11 d depicts a controller in some embodiments.

FIG. 11 e depicts power module comprising ADC circuitry and ZCDcircuitry coupled to the controller in some embodiments.

FIG. 12 is a block diagram of an exemplary digital device.

FIG. 13 depicts a simulated feeder diagram in some embodiments

FIG. 14 is a block diagram of an exemplary switch-controlled voltagesource which may be coupled to a distribution power network in someembodiments.

FIG. 15 is a method of multiple switch-controlled voltage sourcesoperating with different delays in some embodiments.

FIG. 16 depicts a block diagram of a pole top voltage source includingof a plurality of switch-controlled voltage sources in some embodiments.

FIG. 17 is a flow chart of a method for controlling a plurality ofswitch-controlled voltage sources by a processor in some embodiments.

FIG. 18 depicts a simulation of voltage performance of nodes (i.e.,switch-controlled voltage sources) on a primary feeder at different timewithout ENVO in some embodiments.

FIG. 19 depicts a simulation of voltage performance of nodes on aprimary feeder at different time with ENVO in some embodiments.

FIG. 20 depicts a control approach by an aggregated controller perswitch-controlled voltage sources where variable Q (e.g., adjustedvoltage such as, for example, kVAR) is injected over a fixed timeinterval until convergence occurs in some embodiments.

FIG. 21 depicts a simulation of a load voltage response to an inputvoltage step decrease in some embodiments.

FIG. 22 depicts a simulation of a load voltage response to a load stepincrease in some embodiments.

FIG. 23 depicts a control approach by an aggregated controller perswitch-controlled voltage sources where fixed Q (e.g., adjusted voltagesuch as, for example, kVAR) is injected over a variable time interval insome embodiments.

FIG. 24 depicts a simulation of a load voltage response to an inputvoltage step decrease in some embodiments.

FIG. 25 depicts a simulation of a load voltage response to a load stepincrease in some embodiments.

FIG. 26 is a circuit diagram of an exemplary switch-controlled VARsource including a harmonic management block (HMB) in some embodiments.

FIG. 27 is a diagram of an HMB that is configured to add a resistor whena voltage is greater than a resonance threshold in some embodiments.

FIG. 28 is a flowchart for altering or eliminating resonance utilizingHMB within the switch-controlled VAR source in some embodiments.

FIG. 29 is a diagram of an HMB that is configured to isolate resonancewhen voltage is greater than at least one resonance threshold in someembodiments.

FIG. 30 is a flowchart for isolating resonance utilizing the HMB withinthe switch-controlled VAR source in some embodiments.

FIG. 31 is a diagram of an HMB that is configured to “detune” (e.g.,shift) resonance through engagement or disengagement of one or morecapacitors and/or inductors of a switch-controlled VAR source (asdescribed herein) when voltage is greater than at least one resonancethreshold in some embodiments.

FIG. 32 is a flowchart for “de-tuning” resonance utilizing the HMBwithin the switch-controlled VAR source in some embodiments.

FIG. 33 depicts a HMB in series with an inductive module and acapacitive module of one or more switch-controlled VAR sources in someembodiments.

FIG. 34 depicts a transformer coupled to an HMB and an optionalinductive module, the HMB being further coupled to the capacitive modulein some embodiments.

DETAILED DESCRIPTION

New requirements for distribution dynamic voltage control are emerging,driven by distribution renewable energy penetration and the need toincrease grid capacity without building new lines or infrastructure.Applications such as Conservation Voltage Reduction (CVR) and Volt VAROptimization (VVO) promise 3-5% increase in system capacity, simply bylowering and flattening the voltage profile along a distribution grid.To achieve CVR and VVO in the prior art, improvements to the power gridare slow in operation, difficult to model due to increased complexity ofthe overall system, require considerable back end infrastructure (e.g.,modeling, and a centralized, computation and communication facility),are expensive to install in sufficient numbers to improve performance,and difficult to maintain. Further, conventional VVO schemes realizepoor voltage regulation due to few control elements and poor granularresponse.

In various embodiments discussed herein, line voltage may be regulatedat or near every customer point (i.e., at the load along a distributionpower grid). For example, a utility may install a shunt-connected,switch-controlled volt-ampere reactive (VAR) source at each customerlocation. Each shunt-connected, switch-controlled volt-ampere reactive(VAR) source may detect a voltage proximate to the device and make adetermination to enable a VAR compensation component (e.g., capacitor(s)and/or inductor(s)) to regulate voltage on the network. The plurality ofshunt-connected, switch-controlled volt-ampere reactive (VAR) sources,switching independently, may operate collectively to flatten the voltagecurve (e.g., voltage impact along a medium voltage distribution feederstarting from a substation) along a power network. The plurality of VARsources may be controlled to prevent fighting between sources, whileallowing connected points to reach a desired voltage set point with muchhigher granularity and accuracy.

If distributed VAR compensation is implemented, the utility may realizeseveral benefits. For example, a desired voltage profile may bemaintained optimally along the line even as system configurationchanges, system losses may decrease, and/or system stability andreliability may be improved. New cascading grid failure mechanisms, suchas Fault Induced Delayed Voltage Recovery (FIDVR) may also be avoidedthrough the availability of distributed dynamically controllable VARs.

In various embodiments, distributed fast voltage controllers and/orcompensators at or near a power network edge provides a solution that isable to act autonomously on local information with little to noinfighting. This approach may remove uncertainty about the voltagevariations at a range of nodes, flatten the voltage profile along theedge of the network, and allow a Load Tap Changer (LTC) to drop thevoltage to the lowest level possible.

FIG. 1 a depicts a typical distribution feeder 106 fed from a singlesubstation 102 in some embodiments. Standard design practice involvesthe use of load tap changing (LTC) transformers 104 at substations 102,with fixed and switchable medium voltage capacitors on the feeder. FIG.1 depicts a series of houses (i.e., loads) 110, 112, 114, and 116 thatreceive power from various distribution feeders coupled to the primaryfeeder 106 (e.g., distribution feeders separated from the primary feederby transformers 108 a-d). In the prior art, as the distance from thesubstation 102 increases, utility voltage 118 along the primary feeder(e.g., medium voltage distribution feeder 106) decreases.

In the prior art, load tap changers, slow acting capacitor banks, andline voltage regulators may be sporadically placed along one or moreprimary feeders 106 to improve voltage range. Without ConservationVoltage Reduction or CVR, the first houses 110 have a required utilityvoltage of approximately 124.2 volts. Houses 112 have a significantlyreduced utility voltage of approximate 120-121 volts. Houses 114 furtherhave a required voltage between 115 and 116 while houses 116 have arequired voltage between 114 and 115.

FIG. 1 b depicts a distribution feeder 106 fed from a single substation102 and including a plurality of edge of network voltage optimization(ENVO) devices 120 a-d in some embodiments. In various embodiments, VARcompensators (e.g., or any VAR source such as a PV inverter capable ofVAR control), including, for example, ENVO devices 120 a-d, may beplaced at or near any number of the loads (e.g., houses 110, 112, 114,and 116). As a result, the overall voltage range may be flattened alongthe distance from the substation 102 thereby saving energy, increasingresponsiveness, and improving overall control along longer distributionfeeders. In order to avoid infighting between one or more VAR sources,the action of switching (e.g., the timing of switching or the point atwhich VAR compensation is engaged/disengaged) may be different betweenall or a portion of the VAR sources.

The VAR source may each act (e.g., activate or deactivate one or moreVAR components such as a capacitor and/or inductor) quickly andindependently, based at least on voltages proximate to the VAR sources,respectively, to improve voltage regulation and achieve Edge of NetworkVolt Optimization (ENVO) (see ENVO line 122). The ENVO line 122 depictsthat the voltage required for houses 110 is approximately 120 volts.Houses 112, 114, and 116, may require a reasonably flat voltage rangearound approximately 120 volts as well. Those skilled in the art willappreciate that the ENVO line 122 achieves a desired flattening of therequired voltage range while the line indicating utility voltage 118without VAR compensation drops precipitously.

FIG. 1 c depicts another distribution feeder 106 fed from a singlesubstation 102 and including the plurality of ENVO devices 120 a-d insome embodiments. In various embodiments, the ENVO devices 120 a-d mayfurther apply Conservation Voltage Reduction (CVR) to further reducerequired voltage. Line 124 represents the voltage achieved for houses110, 112, 114, and 116 with ENVO devices 132 a-b applying CVR. Forexample, line 124 (like ENVO line 122) is relatively flat. Houses 110and 112 may see approximately 115.2 volts while houses 114 may seeapproximately 115 volts. Further, houses 116 may see 115.4 volts in thisexample. The need to improve system capacity utilization is drivingutilities to implement peak demand reduction and capacity expansionusing techniques such as Conservation Voltage Reduction (CVR) and VoltVAR Optimization (VVO) on non-ENVO devices. Utility companies currentlyapply CVR by receiving information from multiple points in the powergrid, modeling the performance, modeling proposed improvements, andpotentially coordinating activities of capacitor banks along the primaryfeeder on the medium voltage side of the transformers.

Poor controllability of preexisting voltage regulation devices presentssevere challenges to managing voltage variations for system planners andoperators. In particular, poor controllability limits the length of adistribution feeder that can be managed. Poor controllability alsolimits the load variability that can be handled, while keeping allvoltages at end-user locations within bounds.

Further, new trends are seeing an increased use of sectionalizers withbreaker/reclosers to isolate faulted segments and to restore power toother non-faulted line segments, resulting in a significant change inthe network, and voltage profiles. Increased use of networkreconfiguration also makes the task of placing capacitor banks and LTCsat fixed locations more problematic, as the placement has to meet theneeds of multiple configurations. Moreover, the increasing use ofdistributed generation resources, such as roof top photovoltaic (PV)arrays can result in a reversal of power flows locally, with higher linevoltages farther away from the substation, and a breakdown of anyvoltage regulation algorithm that was implemented.

Those skilled in the art will appreciate that VAR sources at or near theedge of the power grid may individually react and correct for higherline voltages that may be a result of PV arrays (e.g., green energyimprovement such as solar panels). These VAR sources may allow both thecustomer and the network to enjoy the benefits of green power withoutsignificantly redesigning or altering the grid to accommodate thechange. Since the voltage along the edge of the network can change dueto a multitude of sources and loads that are distributed along thenetwork, a centralized algorithm, containing a complete state of thegrid including all variables that affect load and input, for slowvoltage control and regulation may not be effective, and with properoperation of a distributed autonomous control algorithm, may also becomeunnecessary.

FIG. 2 is a diagram depicting voltage drop along feeders due to loadswithout the implementation of capacitor banks in the prior art. Asdepicted in FIG. 2, the length of the feeder lines from the substationis limited by the voltage drop. In this example, there is a 10% variancein available voltage. In the prior art, the objective is to keep voltagewithin a broad band. As few control handles are available, only verycourse control is possible. Ideally, the voltage should be closelyregulated to specifications all along the line, including in thepresence of dynamic fluctuations. With few sensors, few correctionpoints, slow communication, and a limited number of operations, priorart control is unable to meet the dynamic control requirements of thenew and future distribution power grid.

By utilizing sporadically placed capacitor banks, voltage regulation maybe implemented to flatten the available voltage range and reduce losses.The capacitor banks may operate based on temperature, for example, orbased on commands from a centralized control facility. When based ontemperature, for example, to avoid interactions and to maximize switchlife of the capacitor banks, switching to activate or deactivate one ormore capacitors is infrequent and slow. Capacitor banks that areoperated under the control a centralized facility may be individuallycommanded to avoid interactions.

In spite of the attempts of controlling voltage through CVR, drops alongthe length of the feeder are only marginally effected by the activationof the capacitor banks. In these examples, the capacitor bank maytypically be switched only three-to-four times per day. The process maybe slow as well. In one example, it may take up to fifteen minutesto: 1) detect conditions; 2) provide the conditions to a centralizedfacility; 3) the centralized facility model conditions and make adetermination to enable or disable a capacitor bank; 4) provide acommand to one or more capacitor banks; and 5) receive the command andperform the switching.

Further, multiple thyristor switched capacitors, if operatingindependently, may fight with each other as each device attempts tocompensate for a locally measured state of the power network. As thethyristor switched capacitors work at cross purposes, they tend toovercompensate and undercompensate while constantly reacting to thecorrections of other thyristor switched capacitors on the power network.The traditional approach of autonomous VAR control to prevent infightingis to use of voltage droop techniques. The use of voltage droop,however, counteracts the objective of CVR which is to maintain a flatand reduced voltage at every load point. As a result, precise and rapidcontrol of voltage at multiple points along the grid cannot be obtainedwith conventional techniques.

FIG. 3 a is a diagram depicting a power distribution grid withshunt-connected, switch-controlled VAR sources at or near each load insome embodiments. Loads are depicted as houses or residences. Inaddition to houses or residences, those skilled in the art willappreciate that the loads can be any loads including, but not limitedto, commercial or industrial establishments. A load is any component,circuit, device, piece of equipment or system on the power distributionnetwork which consumes, dissipates, radiates or otherwise utilizespower. A power distribution grid is an electrical grid, such as aninterconnected network, for delivering electricity from suppliers toconsumers.

In this example, voltage may be regulated at or near the edge of thenetwork thereby allowing edge of network volt optimization (ENVO). Anedge of the network is the portion of a power distribution network thatis proximate to the load that is to receive power. In one example, theload is a customer load. An edge of the network may be on thelow-voltage side of a transformer. For example, the edge of the networkmay comprise one or more feeder lines configured to provide power tomultiple customer loads (e.g., housing residences).

In FIG. 3, a substation provides power to residences (e.g., loads) overa series of regional distribution feeders. Each residence andshunt-connected, switch-controlled VAR source is coupled to the powerdistribution grid. In various embodiments, each shunt-connected,switch-controlled VAR source is configured to detect voltage and adjustnetwork volt-ampere reactive (VARs) based on the detected voltage. Inone example, the shunt-connected, switch-controlled VAR source enables acapacitor and/or an inductor to change (e.g., reduce or eliminate) thereactive power of the power distribution grid thereby regulating voltageof the network (i.e., network voltage). The change in reactive power mayreduce the voltage drop along the distribution feeder.

As discussed regarding FIG. 1, shunt-connected, switch-controlled VARsources may be placed at or near any number of the loads. As a result,the overall voltage range may be flattened along the distance from thesubstation thereby saving energy, increasing responsiveness, andimproving overall control along longer distribution feeders. The VARsource may each act (e.g., activate or deactivate one or more VARcomponents such as a capacitor and/or inductor) quickly andindependently, based at least on voltages proximate to the VAR sources,respectively, acting collectively to improve voltage regulation andachieve ENVO. FIG. 3 depicts that the voltage distribution drop isflatter, for example a +/−2% variance across the network depicted inFIG. 3 without the implementation of the capacitor banks.

FIG. 3 b is another diagram depicting a power distribution grid withshunt-connected, switch-controlled VAR sources at or near each load insome embodiments. In FIG. 3 b, a substation 302 with a load tap changer(LTC) 304 feeds a distribution feeder 306 with line inductance andresistance throughout the distribution feeder 306. Loads 312, 314, 316,and 318 receive power from the distribution feeder 306 via transformers310 a-d respectively. Further, each subfeeder between a transformer andthe loads may include on or more ENVO devices 310 a-e that may beconfigured to act as one or more VAR compensators. In variousembodiments, multiple ENVO devices (e.g., ENVO VAR units) may bedeployed along the length of a typical distribution feeder to flattenthe required voltage and respond to network conditions.

In various embodiments, an optional central controller 320 maycommunicate with one or more of the ENVO devices 310 a-e to receivesensor information and/or behavior information regarding the actions ofone or more ENVO devices 310 a-e. In some embodiments, one or more ofthe ENVO devices 310 may include a communication interface configured tocommunicate with each other and/or the central controller 320. Thecentral controller 320 may, in some embodiments, provide one or more setpoints (discussed herein) that may assist in controlling when one ormore of the ENVO devices 310 become active (e.g., based on comparing oneor more set points to voltage of a portion of the power distributionnetwork. The central controller 320 is further discussed herein.

FIG. 4 a is a circuit diagram of an exemplary switch-controlled VARsource 400 which may be connected in shunt in some embodiments. Theswitch-controlled VAR source 400 may be a part of a large number ofswitch-controlled VAR sources 400 at or near an edge of the powerdistribution grid (i.e., the power network).

At a high level, the switch-controlled VAR source 400 comprises acapacitor 412 (e.g., a VAR compensation component) that is controlledthrough a relay 414 in parallel with a semiconductor switch 416 (e.g.,triac 420—NTC 418 is optional). A processor, such as controller 426, maycontrol the relay 414 and semiconductor switch 416 based on voltage. Forexample, the controller 426 may detect voltage proximate to theswitch-controlled VAR source 400 (e.g., through line 402). Based on thedetected voltage, the controller 426 may enable or disable the capacitorby controlling the relay 414 and semiconductor switch 416. As discussedherein, the relay 414 and semiconductor switch 416 may work together toprotect and prolong the life of various components of theswitch-controlled VAR source 400 during switching operations.

The exemplary switch-controlled VAR source 400 comprises lines 402 and430, fuse 404, an optional inductor 406, resistors 408, 410, 418, 422,and 424, capacitor 412, relay 414, a switch 416 comprising an optionalNTC 418 and triac, controller 426, and power supply unit (PSU) 428.Lines 402 and 430 may be coupled to a feeder such as a feeder on the lowvoltage side of a transformer. In one example, lines 402 and 430 may becoupled to any line or feeder configured to provide power to one or moreloads (e.g., on or at the edge of a network). In some embodiments, theswitch-controlled VAR source 400 is proximate to a residential orcommercial load. For example, the switch-controlled VAR source 400 maybe within a smart meter, ordinary meter, or transformer within proximityto a load. Those skilled in the art will appreciate that theswitch-controlled VAR source 400 may be within any grid asset.

The fuse 404 is configured to protect the switch-controlled VAR source400 from voltage spikes, transients, excessive current, or the like. Thefuse 404 may prevent excessive thermal loading of a failed component,thus allowing the grid to operate even as the VAR source is removed fromthe circuit. The fuse 404 may be any fuse and may be easily replaceable.In some embodiments, if the fuse 404 clears and the switch-controlledVAR source 400 is disconnected from the power distribution network, thepower delivered to the residential and/or commercial loads may not beinterrupted.

The optional inductor 406 and resistor 408 may act as an L-R snubber tocontrol peak inrush currents (e.g., during startup conditions) and tomanage harmonic resonances. In some embodiments, the inductor 406 andresistor 408 may prevent wear on the capacitor 412 and/or the othercircuits of the switch-controlled VAR source 400 caused by changes involtage or power received from the line 402 and/or activation ordeactivation of the switch-controlled VAR source 400.

Those skilled in the art will appreciate that, in some embodiments, theinductor 406 and resistor 408 may reduce susceptibility of the capacitor412 to harmonic resonance. In various embodiments, the switch-controlledVAR source 400 does not comprise the inductor 406 and/or the resistor408.

The capacitor 412 may be any capacitor configured to compensate forreactive power (e.g., VARs). In various embodiments, the relay 414and/or the semiconductor switch 416 may form a switch that completes thecircuit thereby allowing the capacitor 412 to influence reactive powerof the network. In one example, if the relay 414 is open and the triac420 (of the semiconductor switch 416) is deactivated, the capacitor 412may be a part of an open circuit may, therefore, have no effect on thepower distribution gird or the load.

The resistor 410 is an optional bleed resistor. In some embodiments,when the capacitor is disabled or otherwise disconnected by the switch(e.g., via relay 414 and/or semiconductor switch 416), the resistor 410may potentially receive energy from the capacitor 412 thereby allowingthe energy state of the capacitor 412 to decrease.

The relay 414 may be used to reduce losses when the semiconductor switch416 is active. The semiconductor switch 416 may be used to provideprecise and fast response at turn on and turn off. Those skilled in theart will appreciate that any appropriately rated relay (e.g., a testedelectromechanical relay) may be used.

The triac 420 of the semiconductor switch 416 is a gate-controlledthyristor in which current is able to flow in both directions. The relay414 and/or the triac 420 may perform as one or more switches. Forexample, the controller 426 may open the relay 414 and deactivate thetriac 420 to create an open circuit to disconnect the capacitor 412. Invarious embodiments, a pair of thyristor may be used in place of thetriac 420.

Those skilled in the art will appreciate that any switch may be used.For example, a switch S, such as an IGBT, thyristor pair, orthyristor/diode arrangement may also be used. In another example, amosfet or IGBT may be used with a diode in parallel to control thecapacitor 412.

Those skilled in the art will appreciate that the relay 414, the triac420, and NTCs may work together to preserve the life of all or some ofthe components of the switch-controlled VAR source 400. The controller426 may be configured to control the relay 414 and the triac 420 toswitch off the circuit in a manner that avoids transients or otherundesired power characteristics that may impact the lifespan of thecircuit. For example, the controller 426 may ensure that the relay 414is open (e.g., instruct the relay 414 to open if the relay 414 isclosed) before instructing the triac 420 to deactivate (e.g., ½ cyclelater). This process may prevent sparking or arcing across the relay 414and, further, may preserve the life of the relay 414. In someembodiments, the triac 420 may be switched on and, after a sufficientdelay, the relay 414 may be closed. The controller 426 may then instructthe relay 414 to open thereby protecting the one or more components ofthe circuit.

In various embodiments, the switch-controlled VAR source 400 comprisesthe relay 414 but not the semiconductor switch 416. In one example, thecontroller 426 may instruct the relay 414 to open or close therebyenabling or deactivating the capacitor 412. In other embodiments, theswitch-controlled VAR source 400 comprises the semiconductor switch 416but not the relay 414. The controller 426 may similarly control thetriac 420 to enable or disable the capacitor 412.

The optional resistor 418 may be a negative temperature coefficient(NTC) resistor or thermistor. The NTC resistor 418 is a type of resistorwhose resistance may vary with temperature. By controlling the NTCresistor 418, the triac 420 may be activated or deactivated withoutwaiting for a zero voltage crossing of the AC power from the line 402allowing insertion of the VAR source with minimal delay. For example,without the NTC resistor 418, the triac 420 may only be activated whenAC voltage across it crosses zero volts. The NTC resistor 418 may beconfigured such that the triac 420 may be activated at any point withlittle or no undesirable effect (e.g., minimal or reduced inrush).

Resistors 422 and 424 may attenuate the signal from the line 402 to bereceived by the controller 426.

The controller 426 may be configured to determine a proximate voltagebased on the voltage of line 402 and may enable or disable the capacitor412. In various embodiments, the controller 426 is a processor such as amicroprocessor and/or a Peripheral Interface Controller (PIC)microcontroller may detect voltage of the feeder 402.

In some embodiments, based on the voltage, the controller 426 maycontrol the relay 414 and/or the triac 420 to open or close the circuitthereby enabling or disabling the capacitor 412. For example, if thevoltage detected is not desirable, the controller 426 may enable thecapacitor 412 by commanding the triac 420 to activate and/or the relay414 to close. The capacitor 412 may then compensate for reactive power(e.g., regulate network voltage).

Those skilled in the art will appreciate that there may be a delay inthe response of relay 414 (e.g., the relay 414 may be anelectromechanical relay that is slow to react when compared to the triac420). In this example, the command to open the relay 414 may be sent inadvance of the command to deactivate the triac 420. In some embodiments,a command may be sent to turn off the relay 414. Subsequently, after atime delay, the triac 420 may be turned off.

One of the most common failure mechanisms for capacitors on the grid isovervoltage. In some embodiments, the relay 414 and triac 420 may berapidly deactivated when overvoltage is detected thereby protecting thecapacitor(s).

The controller 426 may delay activation or turn off of the switch (e.g.,relay 414 and semiconductor switch 416). In various embodiments, amultitude of switch-controlled VAR sources 400 which react to voltageswithin a power grid. In order to prevent infighting among theswitch-controlled VAR sources 400, one or more of the devices may delayenabling or disabling the VAR compensation component (e.g., capacitor412). In various embodiments, the controller of each switch-controlledVAR source 400 includes a different delay. As a result, eachswitch-controlled VAR source 400 may activate the switch to regulatevoltage at a different time thereby giving each device time to detectvoltage changes that may result from one or more switch-controlled VARsources 400.

Those skilled in the art will appreciate that the delay may be setduring manufacture of the switch-controlled VAR source 400 or may beuploaded from a centralized communication facility. The delay may berandomly set for each different switch-controlled VAR source 400.

The power supply unit (PSU) may adapt the power to be suitable to thecontroller 426. In some embodiments, the controller 426 is supplied frompower supplied by the line 402, batteries, or any other power source.The PSU 428 may be any power supply.

Although FIG. 4 a depicts the line coupled to the resistor 422 as beingon the unprotected side of the fuse 404, those skilled in the art willappreciate that the fuse 404 may protect the controller 426 and PSU 428.For example, the resistor 422 may be coupled to the line 402 via thefuse 404.

In various embodiments, the switch-controlled VAR source 400 may operateboth dynamically and autonomously to regulate voltage and/or compensatefor grid faults. Those skilled in the art will appreciate that theswitch-controlled VAR source 400 may adjust reactive power and thus thenetwork voltage based on detected voltage without detecting or analyzingcurrent. In some embodiments, load current information can be derivedfrom an additional current sensor, or from the smart meter.

In some embodiments, the switch-controlled VAR source 400 may comprisean inductor which may be used to adjust voltage. For example, one ormore inductors may be in place of capacitor 412. In another example, oneor more inductors may be in parallel with the capacitor 412. Theinductor(s) may be coupled to the fuse 404 (or a different fuse) and maybe further coupled to a separate switch. For example, the inductor(s)may be coupled to a relay in parallel with a triac (or mosfet or IGBT)which may perform switching similar to the relay 414 and thesemiconductor switch 416. The controller 426 may enable the inductor anddisable the capacitor 412 by enabling one switch and creating an opencircuit with the other. Similarly, the controller 426 may disable theinductor and enable the capacitor 412 or, alternately, disable both.Those skilled in the art will appreciate that the triac associated withthe inductor may also be coupled to an NTC resistor to allow the triacto be activated at any time.

The switch-controlled VAR source 400 may be shunt-connected to the powerdistribution grid. In one example, the switch-controlled VAR source 400is coupled in shunt via conductive lines 402 and 430 at or proximate toa residence or other commercial load. A shunt connection may be theconnection of components within a circuit in a manner that there aremultiple paths among which the current is divided, while all thecomponents have the same applied voltage.

In one example, a feed line may extend from a transformer to one or moreloads (e.g., residences). The feeder may also be coupled with aswitch-controlled VAR source 400 in shunt. In some embodiments, if theswitch-controlled VAR source 400 fails or was otherwise inoperative, thedelivery of power by the power distribution grid is not interruptedbecause of the shunt connection (e.g., even if the connection to theswitch-controlled VAR source 400 became an open circuit, there may be nointerruption of power between the transformer and the one or more loadsalong the feed line).

In various embodiments, the switch-controlled VAR source 400 may becollocated inside or with a utility meter (e.g., smart meter), so thatinstallation can be piggybacked, saving the utility in totalinstallation and reading costs. The switch-controlled VAR source 400 mayleverage a communication link inside a smart meter to communicate withthe utility, take VAR dispatch or voltage set-point commands, and/orinform the utility of malfunction. Multiple switch-controlled VARsources 400 may be collocated in a common housing and can be mounted onanother grid asset, such as a pole-top or pad-mount transformer. Thismay allow lower cost VAR compensation, reduce the cost of acommunication link, and allow additional value to be derived, such asassessing status and life expectancy of the asset.

In various embodiments, a plurality of switch-controlled VAR sources mayeach comprise a communication module. A communication module is anyhardware configured to communicate wirelessly or by wire with one ormore digital devices or other shunt-connected, switch-controlled VARsources. The communication module may comprise a modem and/or anantenna.

One or more of the switch-controlled VAR sources may receive one or moreset points with which to compare against voltage to assist in thedetermination to engage the VAR compensation component. A set point maybe a predetermined value to improve voltage regulation. The processor ofswitch-controlled VAR source may determine whether to adjust voltagebased on the comparison of the proximate voltage to the set points.Those skilled in the art will appreciate that the set points may bedifferent for different switch-controlled VAR sources.

For example, the switch-controlled VAR source may compare detectedvoltage of a feeder (e.g., proximate voltage) to one or more set pointsto make the determination of whether to activate the capacitor based onthe comparison. For example, if the detected voltage is lower than apreviously received set point, the switch-controlled VAR source mayenable the capacitor to increase voltage. Alternately, if the voltage ishigher than a previously received set point, the switch-controlled VARsource may disable an otherwise active capacitor in order to reducevoltage.

In some embodiments, a communication facility may dispatch and/or updateone or more set points. The switch-controlled VAR sources maycommunicate via a cellular network, power line carrier network (e.g.,via the power grid), wirelessly, via near-field communicationstechnology, or the like. The communication facility may update setpoints of any number of switch-controlled VAR sources at any rate orspeed. For example, the communication facility may update set pointsbased on changes to the grid, power usage, or any other factors.

In some embodiments, one or more of the switch-controlled VAR sourcesmay both receive and provide information. For example, one or more ofthe switch-controlled VAR sources may provide VARs provided, devicestatus, voltage information, current information, harmonic information,and/or any other information to one or more communications facilities(e.g., digital devices).

The information detected, received, or otherwise processed by one ormore of the switch-controlled VAR sources may be tracked and assessed.For example, voltage and/or other power information may be tracked bythe VAR source or a centralized facility to determine usage rates andidentify inconsistent usage. The energy usage at an aggregation point,such as at a transformer where the VAR source is located, may becompared with usage recorded by all the meters connected downstream toidentify potential energy theft. A history of expected usage may bedeveloped and compared to updated information to identify changes thatmay indicate theft, failure of one or more grid components, ordeteriorating equipment. In some embodiments, one or moreswitch-controlled VAR sources may provide information to monitor agingequipment. When changes to voltage or other information indicatesdeterioration or degradation, changes, updates, or maintenance may beplanned and executed in advance of failure.

Those skilled in the art will appreciate that the controller of theswitch-controlled VAR source may enable or disable an inductor. In someembodiments, as discussed herein, the switch-controlled VAR source maycomprise an inductor and a capacitor in parallel. In some examples,based on the comparison of the detected voltage to one or more receivedset points, the controller of the shunt-connected, switch-controlled VARsource may enable or disable the inductor and the capacitorindependently.

In various embodiments, a resistor and/or an NTC may be in series withthe relay 414 which may further protect the circuit and/or extend thelife of the relay 414. For example, a second NTC in series with therelay may prevent current inrush. As a result, the second NTC mayprevent contact erosion and life degradation for the relay.

FIG. 4 b is a graph that depicts activating the semiconductor switchrelative to the relay to engage VAR compensation in some embodiments. Asdiscussed herein, when activating the switch-controlled VAR source 400,the controller 426 may be configured to activate the triac 420 prior toactivating the relay 414. In some embodiments, the controller 426 mayactivate the relay 414 following a predetermined delay. The delay may beany delay. In one example, the controller 426 may receive apredetermined delay (e.g., as software or firmware) during calibrationor installation either before or after manufacture of theswitch-controlled VAR source 400.

As depicted in FIG. 4 b, the triac 420 may be activated at any time.Triac 420 turn-on may cause current to flow through the capacitor 412,and the NTC 418 limits the current value to a safe and/or desirablelevel. If the NTC 418 is warm, a condition that may be determined by thecontroller 426, turn on of the triac 420 may be initiated at the timewhen voltage across it is nearly zero. This would prevent a potentiallydamaging current inrush event. After a delay which may be, for example,approximately a cycle, the relay 414 may be closed. As discussed herein,a second NTC in series with the relay may prevent current inrush, thuspreventing contact erosion and life degradation for the relay. Thoseskilled in the art will appreciate that, with the NTC resistor 418, thetriac 420 may be activated at any time. Further, the relay 414 may beclosed at any time after the triac 420 is active (i.e., the delay may beany length of time).

FIG. 4 c is a graph that depicts deactivating the semiconductor switchrelative to the relay 414 to disengage VAR compensation in someembodiments. As discussed herein, when deactivating theswitch-controlled VAR source 400, the controller 426 may be configuredto ensure that the relay 420 is closed prior to deactivating the triac420. The controller 426 may subsequently deactivate (open) the relay420. In some embodiments, the controller 426 may deactivate the relaytriac 414 following a predetermined delay. The delay may be any delaywhich may be software or firmware received during calibration orinstallation.

As depicted in FIG. 4 c, the relay 420 may be closed at any time. Insome embodiments, the controller 426 confirms that the relay 420 isclosed. If the relay 420 is open, the controller 426 may control therelay 420 to close. After a delay (e.g., after approximately a cycle orany time), the controller 426 may deactivate the triac 420. Thoseskilled in the art will appreciate that the triac 420 may be deactivatedat any point. The controller 426 may control the relay 414 open afterthe triac 420 is deactivated. In some embodiments, the controller 426controls the relay 414 to open after a predetermined delay. The delaymay be equal or not equal to the delay between closing the relay anddeactivating the triac 414.

FIGS. 5 a and 5 b are graphs 500 and 508 that depict a desired voltagerange in relation to set points in some embodiments. In variousembodiments, a switch-controlled VAR source may comprise a single setpoint 502 (e.g., 240 volts). The switch-controlled VAR source may beconfigured to adjust voltage (e.g., through controlling the VARcompensation component) by comparing the detected voltage to the setpoint 502. Threshold 504 and 506 may identify an allowed voltage range(e.g., +/−2 volts) before the switch-controlled VAR source may enable ordisable the VAR compensation component.

Those skilled in the art will appreciate that the thresholds 504 and 506may be equal or unequal. Further, the thresholds 504 and 506 may bechange over time (e.g., through an algorithm that changes based on timeof day, season, temperature, voltage, current, rate of change indetected voltage, or the like).

FIG. 5 b is a graph depicting voltage over time and identifying setpoints 510 and 512 in some embodiments. Set points 510 and 512 bracketthe desired “ideal” voltage (e.g., 240 volts). In various embodiments, aswitch-controlled VAR source may detect a proximate voltage and comparethe detected voltage to set points 510 and 512. If the voltage is higherthan set point 510 or lower than set point 512, the switch-controlledVAR source may enable/disable a VAR compensation component or otherwiseregulate the voltage to make corrections. Although the impact of oneswitch-controlled VAR source may not change the network voltagesignificantly, multiple VAR sources operating autonomously to change thenetwork voltage may regulate the voltage over multiple points. As such,a limited change by many devices may create significant efficiencies andimprovements in distribution with limited additional cost.

In various embodiments, one or more of the switch-controlled VAR sourcesdo not have communication modules but rather may comprise set pointspreviously configured at manufacture. In other embodiments, one or moreof the switch-controlled VAR sources comprise communication modules and,as a result, set points may be altered or updated by otherswitch-controlled VAR sources or one or more central communication andcontrol facilities.

In some embodiments, one or more of the switch-controlled VAR source maycomprise regulation profiles. A regulation profile may comprise a policythat changes one or more set points based on time, proximate conditions,or usage in order to improve conservation. If usage is likely to spike(e.g., based on heat of the day, business loads, residential loads, orproximity to electric car charging facilities), a regulation profile mayadjust the set points accordingly. As a result, set points may bechanged depending upon sensed usage, voltage changes, time of day, timeof year, outside temperature, community needs, or any other criteria.

Those skilled in the art will appreciate that one or more of theswitch-controlled VAR sources may receive regulation profiles at anytime over the communications modules. In some embodiments, one or moreof the switch-controlled VAR sources may not comprise a communicationmodule but may still comprise one or more regulation profiles which mayhave been previously configured.

FIG. 6 is a flow chart for voltage regulation by a switch-controlled VARsource in some embodiments. In step 602, the switch-controlled VARsource may receive a first set point. In some embodiments, theswitch-controlled VAR source comprises a communication module that mayreceive the set point from a digital device (e.g., wirelessly or througha communication module of a smart meter), from another shunt-connected,switch-controlled VAR source (e.g., through near field communication),power line carrier communication, or the like. The set point mayactivate the switch-controlled VAR source to enable VAR compensation or,in some embodiments, the set point may be a voltage set point which maybe compared to a detected proximate voltage.

In some embodiments, the utility may include a VAR source server orother device configured to communicate with different VAR sources (e.g.,via WiFi, cellular communication, near field communication, wired, orpower line carrier). In various embodiments, the VAR source server maycommunicate with one or more other servers to communicate with the VARsources. For example, the VAR source server may communicate throughsmart meters or servers that communicate with smart meters. One or moresmart meter may comprise a VAR source or otherwise communicate with oneor more VAR sources.

The first set point (e.g., a voltage set point) may be a part of aregulation profile. In one example, a plurality of regulation profilesmay be received by the switch-controlled VAR source either duringmanufacture or through a communication module. Each regulation profilemay comprise one or more different set points to improve powerdistribution and/or efficiency based on a variety of factors (e.g., timeof day, history of usage, type of load, green energy production, and thelike). In various embodiments, the processor of the switch-controlledVAR source may switch regulation profiles based on detected voltage,rate of change of voltage, communication with other switch-controlledVAR sources, communication with a VAR source server, temperature, timeof day, changes to the grid or the like. Once implemented from theregulation profile, the processor of a switch-controlled VAR source willcontinue to detect proximate voltage and compare the voltage to the newset point(s) in order to determine whether a VAR compensation componentshould be enabled or disabled.

In step 604, the controller 426 (i.e., processor) detects proximatevoltage at the edge of the network (e.g., near a load of the powergrid). Proximate voltage is the voltage received from line 402 (e.g.,the voltage at the point the line 402 is coupled to a feeder line orgrid asset. The proximate voltage may be the voltage of where theshunt-connected, switch-controlled VAR source 400 is coupled in thepower distribution grid at the time of voltage detection.

In some embodiments, the switch-controlled VAR source may detect voltagethrough another switch-controlled VAR source or a grid asset. In someembodiments, a smart meter, transformer, or other power device maydetect voltage. The switch-controlled VAR source may receive thedetected voltage from the other device or intercept the detected voltageat or during transmission.

In step 606, the controller 426 may compare the detected proximatevoltage to any number of set points to determine if the VAR compensationcomponent may be enabled or disabled. As discussed herein, thecontroller 426 may control a switch (e.g., relay and/or semiconductorswitch) to enable or disable one or more capacitors and/or one or moreinductors based on the comparison. Those skilled in the art willappreciate that the determination to enable or disable the VARcompensation component may be made by the processor of theswitch-controlled VAR source as opposed to a centralized facility. Thedetermination may be made autonomously and independent of otherswitch-controlled VAR sources. Achieving an overall control objectivemay be achieved with the concurrent operation of other similar VARsources.

Through the operation of any number of switch-controlled VAR sourcesoperating to regulate voltage within the desired range, voltageregulation of the network may be achieved. Further, the voltage rangemay be controlled within a desired narrow range, and may further becapable of dynamically responding to changes along one or moredistribution lines and/or feeders.

In step 608, the controller 426 may delay switching the VAR compensationcomponent for a predetermined time. As discussed herein, in order toavoid infighting between any number of switch-controlled VAR sources,one or more of the switch-controlled VAR sources may delay switching fora predetermined time. The time of delay may be different for differentswitch-controlled VAR source. For example, even if a firstswitch-controlled VAR source detects the need to regulate voltage, thefirst switch-controlled VAR source may wait until after a secondswitch-controlled VAR source has made a similar determination andenabled VAR compensation. The first switch-controlled VAR source maydetect the change in the network and make another determination whetherto further enable additional VAR compensation. As a result, multipleswitch-controlled VAR source may not constantly correct and re-correctchanges in network voltage caused by other switch-controlled VARsources.

The delay time may be updated by the VAR source server, otherswitch-controlled VAR sources, or be a part of the regulation profile(e.g., which may comprise multiple different delay times depending onthe need). In some embodiments, if detected voltage is changing at asubstantial rate, the delay time may be accelerated. Those skilled inthe art will appreciate that there may be many different ways toprovide, update, and/or alter the delay time of a switch-controlled VARsource.

In step 610, after detecting and determining a need to change thenetwork voltage and waiting the delay time, the switch-controlled VARsource may again detect any changes to the voltage and compare thechange against one or more of the set points. If there remains adecision in step 612 that is consistent with the previous determinationin step 606 (e.g., that the VAR compensation component should be enabledor disabled), then the switch-controlled VAR source may adjust thenetwork voltage by engaging a switch to enable or disable the VARcompensation component.

In one example, if the proximate voltage is above a first set point, thecontroller 426 may control the relay 414 and the triac 420 to eitherform the connection to the line 402 or to confirm that the relay 414 isclosed and/or the triac 420 is enabled. If the proximate voltage isbelow the second set point, the controller 426 may control the relay 414and the triac 420 to either open the connection to the line 402 or toconfirm that the relay 414 is open and/or the triac 420 is disabled.

In some embodiments, each of the plurality of shunt-connected,switch-controlled VAR sources may increase leading volt-ampere reactiveif the set point is higher than the detected proximate voltage anddecrease leading volt-ampere reactive if the set point is lower than thedetected proximate voltage.

In some embodiments, the controller 426 may enable or disable aninductor based on the comparison of the detected proximate voltage tothe set points. For example, based on the comparison, the controller 426may disable the capacitor and enable an inductor (e.g., the controller426 may control the relay 414 the triac 520 to create an open circuit todisable the capacitor while controlling another relay and another triacto enable the inductor to regulate voltage).

In various embodiments, voltage may be tracked over time. In someembodiments, the controller 426 may track the detected proximate voltageover time and provide the information to another switch-controlled VARsource and/or a digital device. For example, one switch-controlled VARsource may be in communication with any number of otherswitch-controlled VAR source (e.g., in a pole top enclosure). The one ormore switch-controlled VAR sources may be a part of any grid asset suchas a substation or transformer.

In some embodiments, the tracked detected voltage may be assessed and/orcompared to a voltage history. The voltage history may be a history ofpast usage or may indicate an expected usage. In various embodiments,the controller 426 or a digital device may detect a failing grid assetbased on the comparison. For example, the expected output and/or inputof a grid asset may be determined and compared to the tracked detectedproximate voltage. If the currently detected proximate voltage and/ortracked detected proximate voltage are not within the expected range,the tracked detected proximate voltage may be reviewed to determine if agrid asset has failed or is deteriorating. As a result, deterioratingequipment that may need to be replaced or receive maintenance may beidentified and budgeted before performance significantly suffers therebyimproving efficiency in both power delivery and upkeep of thedistribution power grid.

Those skilled in the art will appreciate that potential theft may beidentified. In various embodiments, each switch-controlled VAR sourcemay detect and track voltage. The tracked voltage may be logged and/orprovided to a VAR source server (e.g., via the communication module orantenna of another digital device such as a smart meter). The VAR sourceserver may, for example, track voltage identified by all of theswitch-controlled VAR sources along a feeder line and compare thevoltage to consumption as tracked by the utility (e.g., via smartmeters). Based on the comparison, theft may be detected. Further, basedin part on the effect of any number of switch-controlled VAR sources,the theft may be localized for further investigation.

As suggested herein, massively distributed dynamically controllable VARsource strategy leverages other costs that a public utility is alreadybearing. For example, a switch-controlled VAR source may be locatedinside a smart meter or may be co-located with a smart meter so that theinstallation can proceed concurrently with meter installation orreading/servicing. These meters sense voltage and current to calculatethe power consumption of the load, and have communications to relay theinformation to a central data repository. The cost of installing theseis already built into the meter cost.

A simple communication mechanism with the meter may allow communicationbetween the meter and the switch-controlled VAR source (e.g., forreporting to the utility on status, receiving set points, receivingdelay times, and/or for taking commands to activate). In someembodiments, the load current measurement inside the smart meter may becommunicated to the switch-controlled VAR source for use in thedetermination for voltage regulation.

In various embodiments, a meter switch-controlled VAR source may be verycompact and ultra low-cost. In some embodiments, a typical rating may be500 VARs at 240 volts, corresponding to 2.1 Amperes of capacitivecurrent. This may be approximately the VAR drop across the leakageimpedance of a 5% impedance transformer supplying 10 kW to a customer.Utility networks and asset loading calculations may be done on astatistical basis, assuming a load diversity factor. If all the meters(e.g., 10,000) on a distribution circuit have switch-controlled VARsources, then there may be 5 MVARs of dynamically controllable VARs onthat line, deployed on a per phase basis. Raising the compensation perswitch-controlled VAR source to 1000 VARs, for example, may only raisecost marginally, but may provide 10 MVARs of dynamic VAR compensation.

In various embodiments, the switch-controlled VAR source may beintegrated into or be alongside any utility asset, such as a pole-mounttransformer or lighting pole. As discussed herein, communicationcapability is not a requirement for switch-controlled VAR sourceoperation, but may augment the ability to take dispatch instructions andto communicate status to the utility. A possible implementation would beto bundle multiple switch-controlled VAR sources into a common housingand locating the bundle within or proximate to a transformer supplyingmultiple residential or commercial loads. The bundle may be connected tothe transformer on the low-voltage side thereby minimizing or reducingrequirements for BIL management on the switch-controlled VAR sources.

Those skilled in the art will appreciate that the bundling may allowintegration of a single communication module with multipleswitch-controlled VAR sources, thereby allowing greater cost savings.This class of device may be measured in cost as a ratio of the dollarsof cost of the actual device to the kiloVARs delivered ($/kVAR). Thisbundling may also allow the use of a single power supply and controllerand provide reliable information on the switching behavior of thedifferent switch-controlled VAR source.

In a bundled unit, it may be possible to minimize or reduce impact ofharmonics on the grid. This implementation may maintain the basicfeatures of the single user units, however, the bundle may provide morevalue to utility customers by integrating current and temperaturemeasurement into the unit, using transformer loading and temperatureexcursions to calculate impact on transformer life, and/or communicatingtransformer status to the utilities. The bundled switch-controlled VARsource implementation, particularly when located in close proximity topole-top or pad-mount transformers as conventionally used in the utilityindustry, may offer high value to the utility by performing a functionof dynamic volt-VAR optimization, and in addition, serving as an assetmonitor for the millions of transformers located on the distributionnetwork.

In various embodiments, in order to avoid multiple switch-controlled VARsources from adjusting and readjusting the reactive power based onchanges perceived by other switch-controlled VAR sources, one or morecontrollers may activate or deactivate different switch-controlled VARsource based on a different detected voltage. For example, differentswitch-controlled VAR sources may activate and/or deactivate based ondifferent set points. The different set points may be provided by one ormore remote digital devices. In some embodiments, one or moreswitch-controlled VAR sources may adjust set points (e.g., alter the setpoint by a randomly determined amount) to establish a different setpoint.

The switch-controlled VAR source may perform reactive power compensationbased only on measured line voltage, and not load or line current. Insuch an embodiment, the switch-controlled VAR source may not performpower factor correction. In another embodiment, one may also look at theline current and voltage to assess the level of VAR correction requiredand may operate to bring customer load power factor to unity. Powerfactor correction may not manage reactive power for grid voltageregulation. In some embodiments, a current sensor on the medium voltageline can provide information to correct for the power factor on theprimary medium voltage line, thus reducing overall system losses. Thoseskilled in the art will appreciate that power factor correction is oftenused to reduce penalties, and may reduce energy supplied by the utilityto some extent (if loads have a significant lagging power factor). Inother embodiments, the switch-controlled VAR source may detect current(e.g., via a meter, grid asset, or assessment by the controller 524) andperform power factor correction in addition to voltage regulation usinga weighting algorithm. The multiplicity of VAR sources used may allowfor simultaneous optimization of several objectives such as voltageregulation, as well as load and line power factor.

FIG. 7 is a time sequence of events of network regulation with twoswitch-controlled VAR sources in some embodiments. In variousembodiments, the first and second switch-controlled VAR sources may beproximate to each other (e.g., coupled to the same or related feederline). Changes to voltage caused by one switch-controlled VAR source maybe detected and reacted to by the other switch-controlled VAR source. Asa result, to avoid infighting (e.g., constant correcting andre-correcting voltage in view of other switch-controlled VAR sourceactions), the switching process for one or more of the switch-controlledVAR sources may be delayed by a different delay time. As a result, evenif the first switch-controlled VAR source originally determined toenable the VAR compensation component based on the detected voltage, thefirst switch-controlled VAR source may wait the delay time therebygiving the second switch-controlled VAR source an opportunity to correctvoltage. If the action of the second switch-controlled VAR source wassufficient, then the first switch-controlled VAR source may detect thechange and not perform any switching action.

In step 702, the first switch-controlled VAR source detects a firstvoltage proximate to a first edge of the network. In some embodiments,the first switch-controlled VAR source detects a voltage at a particularload on the low power side of a transformer. In step 704, the firstswitch-controlled VAR source may compare the first proximate voltage toa set point to determine if the VAR compensation component of the firstswitch-controlled VAR source should be enabled. In step 706, theswitch-controlled VAR source may delay switching to engage the VARcompensation component for a first predetermined time (i.e., for a firstdelay).

In step 708, the second switch-controlled VAR source detects a secondvoltage proximate to a second edge of the network. In some embodiments,the second switch-controlled VAR source detects a voltage at aparticular load on the low power side of a transformer. In one example,both the first and second switch-controlled VAR source may be coupled tothe same feeder line and/or on the same side of the same transformer. Instep 710, the second switch-controlled VAR source may compare the secondproximate voltage to a set point to determine if the VAR compensationcomponent of the second switch-controlled VAR source should be enabled.In step 712, the switch-controlled VAR source may delay switching toengage the VAR compensation component for a second predetermined time(i.e., for a second delay).

The first and second delay may be for different periods of time. As aresult, each switch-controlled VAR source may delay acting on thecomparison of the detected proximate voltage to one or more set pointsuntil other switch-controlled VAR sources have had an opportunity tocorrect voltage of the network. If, after the predetermined time, theinitial determination is still necessary (e.g., the proximate voltagehas remained unchanged or still outside of the set point(s) afterexpiration of the delay time), then a switch-controlled VAR source maycontrol a switch to engage or disengage the VAR compensation component.

In various embodiments, delays may be used to avoid infighting betweentwo or more switch-controlled VAR sources. The delays may be updatedand/or communicated by another digital device (e.g., wirelessly, overpower line carrier, or via a smart meter).

As discussed herein, the delay time may be altered based on conditionsof the power network. For example, if the rate of change of voltage,current, or any power characteristic is significant, the delay time maybe shortened or extended. In some embodiments, there are different delaytimes for different switch-controlled VAR sources, however, all of thedelay times may be changed in the similar manner (e.g., shortened orextended) under similar conditions.

In step 714, the second switch-controlled VAR source detects proximatevoltage after the second delay time (e.g., after the secondpredetermined delay). In various embodiments, the switch-controlled VARsources detect proximate voltage at predetermined times or continuously.Once the delay is expired, the controller of the secondswitch-controlled VAR source may retrieve the last detected voltage ordetect voltage of the line. In step 716, the second switch-controlledVAR source determines whether to enable VAR compensation based oncomparison of the last detected proximate voltage to one or more setpoints.

In step 718, if, based on the comparison, the second switch-controlledVAR source determines to enable the VAR compensation component, thesecond switch-controlled VAR source may adjust the network voltage(e.g., by regulating VAR).

In various embodiments, the first switch-controlled VAR source maycontinue the delay before switching the related VAR compensationcomponent. The first switch-controlled VAR source may detect a change involtage caused by the action of the second switch-controlled VAR source.If, after the first delay, the newly detected proximate voltage is stilloutside a range established by one or more set points, the firstswitch-controlled VAR source may engage the VAR compensation component.If, however, after the delay, the action of the second switch-controlledVAR source improves network voltage (e.g., the newly detected voltage iswithin a range of the one or more set points), the firstswitch-controlled VAR source may not take further action.

In step 720, the first switch-controlled VAR source detects proximatevoltage after the first delay time (e.g., after the first predetermineddelay). In one example, once the delay is expired, the controller of thefirst switch-controlled VAR source may retrieve the last detectedvoltage or detect voltage of the line. In step 722, the firstswitch-controlled VAR source determines whether to enable VARcompensation based on comparison of the last detected proximate voltageto one or more set points.

In step 724, if, based on the comparison, the first switch-controlledVAR source determines to enable the VAR compensation component, thefirst switch-controlled VAR source may adjust the network voltage (e.g.,by regulating VAR).

Those skilled in the art will appreciate that the voltage set points maybe preconfigured. In some embodiments, one or both switch-controlled VARsources may comprise communication module(s) configured to receive setpoint(s). In one example, a switch-controlled VAR source may receive newset points that may replace or supplement previously received and/orpre-existing set points.

Although only two switch-controlled VAR sources are discussed regardingFIG. 7, those skilled in the art will appreciate that there may be anynumber of switch-controlled VAR sources working to adjust the networkvolt ampere reactive (e.g., each may have different delays to preventinfighting).

FIG. 8 is a graph that depicts a typical voltage profile at variousnodes in the prior art. Colored dots represent various times of the day.With the prior art's approaches, a VVO or CVR solution is limited by thehighest and lowest voltage nodes.

FIG. 9 is a graph that depicts relatively flat voltage profile atvarious nodes in some embodiments realized with 240 switch controlledVAR sources operating to regulate the voltage along the edge of thedistribution feeder. Edge of Network Voltage Optimization (ENVO) asdiscussed herein may be achieved through dynamic, autonomous actions ofmultiple switch-controlled, VAR sources at or near the edge of thenetwork. The switch-controlled, VAR sources may react automatically andautonomously (e.g., independent switching to enable or disable a VARcompensation component) to varying levels of loading on the feeder,maintaining the edge of network voltage all along the feeder within atight regulation band.

This regulation may be maintained automatically even as heavily loadedregions shift randomly and stochastically over the design range for thefeeder. In some embodiments, what results is a remarkably flat voltageprofile across all measured edge of network points which isunprecedented under current technology. The graph shows voltage withENVO that is relatively flat, voltage without ENVO that dropssignificantly, and a relatively flat voltage utilizing ENVO in CVR mode.The voltage spread is seen to reduce from +1/−5% without compensation to+/−1% with ENVO when operated with the same feeder and the same load.

FIG. 10 is a graph that depicts a dynamic response of the ENVO system toline voltage changes (which can be caused by solar PV plants), as wellas to step changes in line loading in some embodiments. In both cases,the voltage across the entire line is seen to quickly stabilize,demonstrating the high speed response. It may be noted that the initialchanges to the lines beginning at time 0 and the changes to the linesafter time 2.5 are a part of the set up and deactivation of asimulation.

FIG. 10 shows the ability to implement CVR with ENVO compensation,realizing a flat and reduced voltage profile along the length of thefeeder. Coordinating with an LTC at the substation, it is seen that theedge of network voltage may be reduced by 3-6% (e.g., 4%) giving areduction of 3.2% of energy consumed under a typical CVR factor of 0.8.This level of performance is simply not possible with conventional VVCor VVO solutions in the prior art.

The ENVO system operation may not be generally impacted by networkconfiguration or by direction of power flows (e.g., from sporadic greenenergy generation), as are other VVO methods that rely on concentratedpositions of devices that may work for one configuration but notanother. As a result, network reconfiguration due to Fault DetectionIsolation and Restoration (FDIR) schemes may not negatively impact theENVO. Further, operation of tap changers may be simplified, as can theimplementation of CVR functionality due to the increased control of theedge of network voltage profile. Moreover, the ENVO system sources mayrespond rapidly (e.g., within or much less than a cycle such as equal orless than 16.6 ms), to system faults helping to avert cascading failuressuch as Fault Induced Delayed Voltage Recovery or FIDVR events.

While no communication is required to achieve a flatter voltage profilealong the entire length of the line, in various embodiments, inexpensiveslow-speed variable-latency communications may allow advanced functionssuch as VVO and CVR (e.g., through set points), without the complexityof current VVO systems, at a cost that is substantially lower. Further,significant opportunities may exist to leverage existing investments incommunications and other grid infrastructure to further reduce the totalcost of ownership.

In mature markets, such as in the US, the ENVO system may implement acost-effective distribution automation technology with a strong returnon investment (ROI). In some embodiments, the ability to dynamicallyand/or automatically compensate for line-voltage drops all along thefeeder allows building longer feeders, allows an increase in thecapacity of existing feeders, particularly in rural areas, andsignificantly reduces the number of tap changing regulators needed aswell as reduces the frequency of tap changes. It may also allow easierintegration of distributed generation resources and may counteract therapid voltage fluctuations caused by green energy generation (e.g.,unpredictable clouds or wind change).

FIG. 11 a is another circuit diagram of a plurality of switch-controlledVAR sources that may be within or next to a pole top transformer or anygrid asset in some embodiments. FIGS. 1 b-3 focus on different portionsof the circuit diagram of FIG. 11 a. In various embodiments, anytransformer (e.g., pole top transformer), smart meter, meter, or gridasset may comprise one or more VAR sources. Each of a plurality of VARsources may make determinations and adjust voltage autonomously fromothers in the pole top transformer. In some embodiments, a plurality ofVAR sources may share any number of components, including, for example,a controller and/or a power supply unit.

In various embodiments, one or more controllers may control two or moreof the VAR sources in a pole top transformer to coordinate voltageadjustment. For example, a single controller may detect proximatevoltage, compare the voltage against one or more set points, determine avoltage adjustment, and determine which of the VAR sources should beenabled (or disabled) to achieve the desired effect and provide theappropriate commands.

In some embodiments, one or a subset of the VAR sources may comprise oneor more inductors in parallel with one or more capacitors. Those skilledin the art will appreciate that the inductor may be enabled whennecessary to adjust voltage. In other embodiments, there may any numberof inductors and any number of capacitors in any number of theshunt-connected, switch-controlled VAR sources.

FIG. 11 a depicts a switch-controlled VAR source 1102, a plurality ofswitch-controlled VAR sources 1104, a controller 1106, and a powermodule 1108. The switch-controlled VAR source 1102 may be any one of theplurality of switch-controlled VAR sources 1104. The switch-controlledVAR source 1102 may be similar to the switch-controlled VAR source 400.The plurality of switch-controlled VAR sources 1104 may comprise anynumber of switch-controlled VAR sources. The controller 1106 may be amicroprocessor, PIC, or any processor. The power module 1108 may performvoltage detection and/or zero crossing threshold detection (ZCD).

Those skilled in the art will appreciate that the circuits depicted inFIG. 11 may be a part of any device or combination of devices and is notlimited to pole top transformers. For example, there may be a pluralityof switch-controlled VAR sources 1104, controllers 1106, and/or powermodules 1108 associated with any grid asset or as a standalone unit(e.g., coupled to a feeder line in shunt).

FIG. 11 b depicts a switch-controlled VAR source 1102 in someembodiments. The switch-controlled VAR source 1102 may comprise a fuse,capacitor, harmonic sensor, zero voltage detection for ADC circuitry, Isense detection for ADC circuitry, and a relay circuit. Theswitch-controlled VAR source 1102 may be coupled to a feeder in shunt,adjust reactive power, and provide information (e.g., harmonicinformation, ZVD, and/or I sense signals) to the controller 1106. Thetriac and relay circuit may be controlled by signals from the controller1106.

In some embodiments, the harmonic sensor may detect harmonic resonancewhich may be subsequently reduced or eliminated. The I sense detectionfor ADC circuitry and zero voltage detection for ADC circuitry may beused to detect current, harmonics, and/or voltage which may allow thecontroller 1106 to better protect the circuit and make adjustments forvoltage regulation. The relay circuitry may be a part of the switch toenable or disable the capacitor.

FIG. 11 c depicts a plurality of switch-controlled VAR sources 1104 insome embodiments. Each switch-controlled VAR source of FIG. 11 c mayinclude similar or dissimilar components from the otherswitch-controlled VAR sources. For example, one or more of theswitch-controlled VAR sources may comprise an inductor in parallel witha capacitor. A single controller may control one or more of theswitch-controlled VAR sources.

FIG. 11 d depicts a controller 1106 in some embodiments. The controller1106 may control any number of switch-controlled VAR sources 1104. Thecontroller may receive information (harmonic information, ZVD, and/or Isense signals) from one or more of the switch-controlled VAR sources anduse the information to control triacs, relays, and/or reduce harmonicresonance. For example, the controller 1106 may receive and makeadjustments based on voltage detection of only one of the plurality ofswitch-controlled VAR sources 1104. Although only one processor isdepicted in FIGS. 11 a and 11 d, those skilled in the art willappreciate that there may be any number of processors coupled to anynumber of switch-controlled VAR sources.

FIG. 11 e depicts power module 1108 comprising ADC circuitry and ZCDcircuitry coupled to the controller 1106 in some embodiments. The ADCcircuitry and ZCD circuitry may be coupled to the feeder and provideinformation and/or power to the controller 1106. The ADC circuitry andZCD circuitry may provide the controller 1106 power and/or informationregarding voltage. In some embodiments, the controller 1106 controls oneor more of the triacs of the plurality of the switch-controlled VARsources 1102 based on the zero crossing detection.

Those skilled in the art will appreciate that other circuit designs,components, and the like may perform similar functionality or performsimilar results and still be within the invention(s) described herein.

FIG. 12 is a block diagram of an exemplary digital device 1200. In someembodiments, the digital device 1200 may provide set points and/orprofiles to one or more switch-controlled VAR sources. The digitaldevice 1200 may also receive voltage and/or power tracking informationwhich may be used to track usage, identify potential theft, and/ormaintain grid assets. Further, in various embodiments, the digitaldevice 1200 may coordinate and/or control any number ofswitch-controlled VAR sources.

The digital device 1200 comprises a processor 1202, a memory system1204, a storage system 1206, a communication network interface 1208, anoptional I/O interface 1210, and an optional display interface 1212communicatively coupled to a bus 1214. The processor 1202 is configuredto execute executable instructions (e.g., programs). In someembodiments, the processor 1202 comprises circuitry or any processorcapable of processing the executable instructions.

The memory system 1204 is any memory configured to store data. Someexamples of the memory system 1204 are storage devices, such as RAM orROM. The memory system 1204 can comprise the ram cache. In variousembodiments, data is stored within the memory system 1204. The datawithin the memory system 1204 may be cleared or ultimately transferredto the storage system 1206.

The data storage system 1206 is any storage configured to retrieve andstore data. Some examples of the data storage system 1206 are firmwarememory, flash drives, hard drives, optical drives, and/or magnetic tape.In some embodiments, the digital device 1200 includes a memory system1204 in the form of RAM and a data storage system 1206 in the form offlash data. Both the memory system 1204 and the data storage system 1206comprise computer readable media which may store instructions orprograms that are executable by a computer processor including theprocessor 1202.

The communication network interface (com. network interface) 1208 can becoupled to a network (e.g., communication network 164) via the link1216. The communication network interface 1208 may support communicationover an Ethernet connection, a serial connection, a parallel connection,or an ATA connection, for example. The communication network interface1208 may also support wireless communication (e.g., 802.16 a/b/g/n,WiMax). It will be apparent to those skilled in the art that thecommunication network interface 1208 can support many wired and wirelessstandards.

The optional input/output (I/O) interface 1210 is any device thatreceives input from the user and output data. The optional displayinterface 1212 is any device that is configured to output graphics anddata to a display. In one example, the display interface 1212 is agraphics adapter. It will be appreciated that not all digital devices1200 comprise either the I/O interface 1210 or the display interface1212.

It will be appreciated by those skilled in the art that the hardwareelements of the digital device 1200 are not limited to those depicted inFIG. 12. A digital device 1200 may comprise more or less hardwareelements than those depicted. Further, hardware elements may sharefunctionality and still be within various embodiments described herein.In one example, encoding and/or decoding may be performed by theprocessor 1202 and/or a co-processor located on a GPU (i.e., NVidia).

FIG. 13 depicts a simulated feeder diagram 1300 in some embodiments.FIG. 13 comprises a substation 1302 with two feeders including theprimary feeder 1304 and the secondary feeder 1306. Along each feeder,loads and ENVOs are installed after an 8 kV/240V transformer. In thisexample, ENVOs are co-located or located near loads on differentfeeders.

In some embodiments, each ENVO comprises a switch-controlled voltagesource. The switch-controlled voltage source may be similar to theswitch-controlled VAR source 400 of FIG. 4 a. The switch-controlledvoltage source may adjust reactive power, real power, or both. Invarious embodiments, the switch-controlled voltage source is theswitch-controlled VAR source 400 of FIG. 4 a.

In the example depicted in FIG. 13, there is an ENVO located at or nearevery load. In various embodiments, switch-controlled voltage sources orENVOs are not located at or near every load. For example, multiple loadsmay not be at or near a switch-controlled voltage source or ENVO.Further, in some embodiments, one or more switch-controlled voltagesources or ENVOs may be located together (e.g., within a pole top wheremultiple ENVOs may be controlled by a single processor or controller).

In various embodiments, each switch-controlled voltage source or ENVOmay comprise one or more delays to avoid infighting. For example, if avariety of different switch-controlled voltage sources or ENVOs wait fordifferent delay durations before acting, one or more switch-controlledvoltage sources or ENVOs may take the voltage adjustments of otherswitch-controlled voltage source or ENVOs into account before takingaction. As a result hysteresis or bouncing above and below a desirednetwork voltage is reduced or eliminated.

In various embodiments, each switch-controlled voltage source or ENVOmay generate a delay (e.g., with a randomizer) that allows the differentunits to act in concert even if there is no direct communication betweenthe different switch-controlled voltage source and no direct control bya centralized communication facility that synchronizes behavior in realtime by directly commanding the different switch-controlled voltagesource to engage or disengage.

In various embodiments, the different switch-controlled voltage sourcesor ENVOs act independently, however, in the aggregate, the effect is toimprove power and/or voltage across all or part of the distributionpower network.

FIG. 14 is a block diagram of an exemplary switch-controlled voltagesource 1400 which may be coupled to a distribution power network in someembodiments. The switch-controlled VAR source 1400 may comprise ann-cycle delay control module 1402, a slow/fast integral control module1404, “or” modules 1406 a-b, latch 1408, and a VAR compensationcomponent 1410 (could be a capacitor or inductor). In some embodiments,if the measured terminal voltage (V_(PN)) is out of range, the n-cycledelay control block 1402 generates a switching signal to regulatevoltage by switching in or switching out voltage sources (e.g., VARs)after a delay of n-cycles at fundamental frequency:

V _(PN) <=V _(low)(Switch In)

V _(PN) >=V _(high)(Switch out)

The value n may define the switching instant of an individualswitch-controlled voltage source 1400. V_(low) and V_(high) are valuesthat may provide limits for hysteresis control.

The slow/fast integral control block 1404 may work in parallel with then-cycle delay control block 1402. In various embodiments, if themeasured voltage error is either too high or too low then Slow/FastIntegral Control block 1404 may generate a switching signal for fastswitching during transient voltage conditions and slow switching duringsteady state conditions, respectively.

In various embodiments, the n-cycle delay control bock 1402 regulatesline voltage within a regulation range. The n-cycle delay control bock1402 may comprise a voltage detection module 1412 (RMS calculation)coupled to a first high voltage comparator 1414, a first low voltagecomparator 1416, and an n-cycle delay module 1418. The n-cycle delaymodule 1418 is coupled to a second high voltage comparator 1420. An“and” module 1424 a is coupled to both the first and second high voltagecomparators 1414 and 1420. The n-cycle delay module 1418 is also coupledto a second low voltage comparator 1422. An “and” module 1424 b iscoupled to both the first and second low voltage comparators 1416 and1422.

The “and” modules 1424 a and 1424 b are respectively coupled to “or”modules 1406 a and 1406 b, respectively. The “or” modules 1406 a and1406 b are coupled to a latch module 1408 which in turn is coupled to avoltage source 1410 such as, but not limited to, a capacitor or anyother voltage compensation component.

In various embodiments, the voltage detection module 1412 may detect avoltage and provide the detected voltage to the first high voltagecomparator 1414, the first low voltage comparator 1416, and the n-cycledelay module 1418. The voltage detection module 1412 may, in someembodiments, calculate an RMS value or any other value associated withthe detected voltage from the power line. In various embodiments, thevoltage detection module 1412 does not calculate a value of the detectedvoltage.

The first high level comparator 1414 may receive the detected voltage(e.g., any value representing detected voltage) from the voltagedetection module 1412 and compare the detected voltage to a first highvoltage value. The first high voltage value may comprise a set point ormay be determined based on one or more set points received by theswitch-controlled voltage source 1400. If the first high levelcomparator 1414 determines that the detected voltage is greater than thefirst high voltage value, the first high level comparator 1414 mayprovide a first high voltage signal to the “and” module 1424 a.

The first low level comparator 1416 may receive the detected voltage(e.g., any value representing detected voltage) from the voltagedetection module 1412 and compare the detected voltage to a first lowvoltage value. The first low voltage value may comprise a set point ormay be determined based on one or more set points received by theswitch-controlled voltage source 1400. Any number of set point(s) of thefirst low level comparator 1416 may be similar to different than anynumber of set point(s) of the first high level comparator 1414. If thefirst low level comparator 1416 determines that the detected voltage isless than the first low voltage value, the first low level comparator1416 may provide a first low voltage signal to the “and” module 1424 a.

The n-cycle delay module 1418 may be a module that stores and/orgenerates a delay value (e.g., an n-cycle delay value). In someembodiments, the switch-controlled voltage source 1400 comprises or iscoupled to a communications interface (e.g., through integration with asmart meter) which is configured to receive one or more delay values. Invarious embodiments, the switch-controlled voltage source 1400 may bepreconfigured with one or more delay values when the switch-controlledvoltage source 1400 is fabricated. Further, in some embodiments, theswitch-controlled voltage source 1400 may generate one or more delayvalues. For example, the n-cycle delay module 1418 may comprise arandomizer to generate a delay value. Those skilled in the art willappreciate that the n-cycle delay module 1418 may generate a delay overa preset range of values (e.g., the present range of values beingreceived via a communication interface, preconfigured, or generated).

After a delay duration based on the delay value, the n-cycle delaymodule 1418 provides the detected signal to the second high levelcomparator 1420 and the second low level comparator 1422. The secondhigh level comparator 1420 may be similar to or different from the firsthigh level comparator 1414. For example, the second high levelcomparator 1420 may compare the detected voltage to one or more setpoints that is similar or different from one or more set points of thefirst high level comparator 1420. Further, the second low levelcomparator 1422 may be similar to or different from the first low levelcomparator 1422. For example, the second low level comparator 1422 maycompare the detected voltage to one or more set points that is similaror different from one or more set points of the first low levelcomparator 1416.

If the second high level comparator 1420 determines that the detectedvoltage is greater than a second high voltage value (the second highvoltage value being based on one or more set points of the second highlevel comparator 1420), the second high level comparator 1420 mayprovide a second high voltage signal to the “and” module 1424 a.

If the second low level comparator 1422 determines that the detectedvoltage is less than a second low voltage value (the second low voltagevalue being based on one or more set points of the second low levelcomparator 1422), the second low level comparator 1422 may provide asecond low voltage signal to the “and” module 1424 b.

The “and” module 1424 a may receive the first and second high voltagesignals from the first and second high level comparators 1414 and 1420,respectively. The first and second high voltage signals may be similar(e.g., may be the same signal) or different. If both the first andsecond high voltage signals are received by the “and” module 1424 a, the“and” module 1424 a may provide an “off” signal to the “or” module 1406b. The “off” signal may be similar or different from the first and/orsecond high voltage signals.

The “and” module 1424 b may receive the first and second low voltagesignals from the first and second low level comparators 1416 and 1422,respectively. The first and second low voltage signals may be similar(e.g., may be the same signal) or different. If both the first andsecond low voltage signals are received by the “and” module 1424 b, the“and” module 1424 b may provide an “on” signal to the “or” module 1406a. The “on” signal may be similar or different from the first and/orsecond low voltage signals.

The slow/fast integral control 1404 may comprise a mixer 1426 that mixesa set voltage (e.g., Vset) with the detected voltage from the voltagedetector 1412. The mixer 1426 may provide the mixed signal to the scalarmodule 1428. The scalar module 1428 may provide a scaling factor (e.g.,K) the mixed signal. The scaling factor may be, for example, received byan optional communication interface, preconfigured, or generated.

Those skilled in the art will appreciate that the switch-controlledvoltage source 1400 may comprise any number of set points. Any number ofthe set points may be received from a communications interface,preconfigured, and/or generated. In various embodiments, one or more ofthe set points may be altered or updated at any time. In variousembodiments, a processor of the switch-controlled voltage source 1400may be configured to update, modify, or change one or more set points.For example, the processor of the switch-controlled voltage source 1400may perform a learning function to identify likely power scenarios(e.g., a consistent change in voltage or a change in voltage that isperiodic) and change one or more set points to improve efficiency inview of performance of the switch-controlled voltage source 1400 and/orexpected result from any number of other voltage sources (e.g.,capacitor banks and/or other switch-controlled voltage source 1400).

The scalar module 1428 may provide the scaled, mixed signal to theintegration module 1430. The integration module 1430 may integrate anumber of errors and/or number of events whereby the detected voltage isabove or below any number of set points. The integration module 1430 mayprovide a high voltage saturation signal to “and” module 1436 a andprovide a low voltage saturation signal to “and” module 1436 b

The third high voltage comparator 1432 and third low voltage comparator1434 of the slow/fast integral control module 1404 may be configured toreceive the detected voltage (e.g., from the voltage detector 1412). Thethird high voltage comparator 1432 may compare the detected voltage toone or more set points. The one or more set points of the third highvoltage comparator 1432 may be similar to or different from any numberof set points of the n-cycle delay control module 1402 or the third lowvoltage comparator 1434. If the detected voltage is greater and/or equalto one or more set points, the third high voltage comparator 1432 mayprovide a third high voltage signal to the “and” module 1436 a.

The third low voltage comparator 1434 may compare the detected voltageto one or more set points. The one or more set points of the third lowvoltage comparator 1434 may be similar to or different from any numberof set points of the n-cycle delay control module 1402 or the third highvoltage comparator 1432. If the detected voltage is less than and/orequal to one or more set points, the third low voltage comparator 1434may provide a third low voltage signal to the “and” module 1436 b.

The “and” module 1436 a may receive the high voltage saturation signaland the third high voltage signal from the integration module 1430 andthird high level comparator 1432, respectively. The high voltagesaturation signal and the third high voltage signal may be similar(e.g., may be the same signal) or different. If both the high voltagesaturation signal and the third high voltage signal are received by the“and” module 1436 a, the “and” module 1436 a may provide an “off” signalto the “or” module 1406 b. The “off” signal may be similar or differentfrom the high voltage saturation signal and the third high voltagesignal.

The “and” module 1436 b may receive the low voltage saturation signaland the third low voltage signal from the integration module 1430 andthird low level comparator 1434, respectively. The low voltagesaturation signal and the third low voltage signal may be similar (e.g.,may be the same signal) or different. If both the low voltage saturationsignal and the third low voltage signal are received by the “and” module1436 b, the “and” module 1436 b may provide an “on” signal to the “or”module 1406 a. The “on” signal may be similar or different from the highvoltage saturation signal and the third high voltage signal.

If an “on” signal from the “and” module 1436 b and/or the “on” signalfrom the “and” module 1424 b is received by the “or” module 1406 a, thelatch module 1408 may receive a signal from the “or” module 1406 a toactivate (e.g., close the switch) the voltage source 1410. The switchmay comprise a transistor, relay, or any other switch such as, forexample, all or part of semiconductor switch 416 and/or relay 414 ofFIG. 4 a.

If an “off” signal from the “and” module 1436 a and/or the “off” signalfrom the “and” module 1424 a is received by the “or” module 1406 b, thelatch module 1408 may receive a signal from the “or” module 1406 b todeactivate (e.g., open the switch) the voltage source 1410.

Those skilled in the art will appreciate that the latch 1408 may be anykind of latch such as a state device or a flip flop. The “or” modules1406 a-b may comprise, either separately or collectively, any type ofhardware or software to perform “or” logic operations.

Further, those skilled in the art will appreciate that “and” modules1424 a-b and 1436 a-b may comprise, either separately or collectively,any type of hardware or software to perform “and” logic operations.Further, although the voltage source is depicted in FIG. 14 as acapacitor, those skilled in the art will appreciate that any number ofcapacitors, inductors, and/or any other voltage sources may enactedthrough activation of a switch. The switch may also be either softwareor hardware.

In various embodiments, a module may be hardware, software, or acombination of hardware and software. In some embodiments, some of theelements of FIG. 14, such as the n-cycle delay control module 1402 andthe slow/fast integral control module 1404 may be implemented logically,in software, by a processor of the switch-controlled VAR source 1400.Those skilled in the art will appreciate that the various circuits,modules, and gates may be implemented in many ways.

FIG. 14 is one of many possible implementations of delays and control ofone or more voltage sources. Those skilled in the art will appreciatethat there may be any number of comparisons to one or more set pointsover any kind of delay to avoid infighting. For example, there may beany number of switch-controlled VAR sources operating to correct voltageafter a delay. Because the delays of any number or a subset ofswitch-controlled voltage sources are different, the effect may be tocorrect and/or improve power within and/or throughout a powerdistribution network or a feeder without hysteresis. In someembodiments, as corrections occur, any number of switch-controlled VARsources may activate (albeit at potentially different delays) to improvepower asymptotically.

In some embodiments, the switch-controlled voltage source 1400 comprisesor is coupled to a communications interface (e.g., through integrationwith a smart meter) which is configured to receive one or more delayvalues. In various embodiments, the switch-controlled voltage source1400 may be preconfigured with one or more delay values when theswitch-controlled voltage source 1400 is fabricated. Further, in someembodiments, the switch-controlled voltage source 1400 may generate oneor more delay values. For example, the n-cycle delay module 1418 maycomprise a randomizer to generate a delay value. Those skilled in theart will appreciate that the n-cycle delay module 1418 may generate adelay over a preset range of values (e.g., the present range of valuesbeing received via a communication interface, preconfigured, orgenerated).

FIG. 15 is an exemplary method of multiple switch-controlled VAR (alsoin figures) sources operating with different delays in some embodiments.As discussed herein, each switch-controlled VAR source (e.g., the firstand second switch-controlled voltage sources) may comprise all or someof the components of the switch-controlled VAR source 400 as discussedregarding FIG. 4 a. For example, each switch-controlled voltage sourcediscussed with regard to FIG. 15 may comprise a processor, a switch,and/or a voltage compensation component. Each processor may be anyprocessor such as, but not limited to, controller 426 of FIG. 4 a. Eachswitch may be any switch such as, but not limited to optional NTC 418,triac 420, and/or relay 414 of FIG. 4 a. The voltage compensationcomponent may be any voltage source that may compensate for voltage orpower. Each voltage compensation component may be any voltagecompensation component, such as, but not limited to capacitor 412. Thevoltage compensation component may compensate reactive power, realpower, or a combination of real and reactive power of a feeder line,branch, or any portion of a power distribution network.

In step 1502, a first switch-controlled voltage source may generate afirst delay value. In one example, a randomizer of the firstswitch-controlled voltage source may generate a first delay value. Therandomizer may randomly select the first delay value or, in someembodiments, the randomization may be weighted or limited to a range ofdelay values.

In step 1504, a second switch-controlled voltage source may generate asecond delay value. In one example similar to step 1502, a randomizer ofthe second switch-controlled voltage source may generate a second delayvalue. The randomizer may randomly select the second delay value or, insome embodiments, the randomization may be weighted or limited to arange of delay values. The randomizer of the second switch-controlledvoltage source and the randomizer of the first switch-controlled voltagesource may be weighted or limited in a similar or different manner.

Those skilled in the art will appreciate that the delay value may beobtained in any number of ways. A randomizer may generate the delayvalue or may only be a part of the overall process of delay valuegeneration. In some embodiments, the delay value is selected from a setof delay values based on a range of delay values.

In various embodiments, instead of generating the delay value, the firstand/or second switch-controlled voltage source may obtain one or moredelay values through receiving the delay values via an optionalcommunication interface (e.g., from a centralized communication facilityor through near field communications between one or moreswitch-controlled voltage sources). The first and/or secondswitch-controlled voltage source may also be preconfigured (e.g., duringor after manufacture) with one or more delay values. In variousembodiments, each switch-controlled voltage source comprises memorycoupled to the respective processor. In some embodiments, the processorobtains the one or more delay values from memory and/or from storage.

As discussed regarding FIG. 14, each switch-controlled voltage sourcemay comprise any number of delay values. For example, eachswitch-controlled voltage source may comprise an n-cycle delay valueand/or an integrator that may function to delay immediate implementationof a voltage compensation component.

In step 1506, the first switch-controlled voltage source monitors afirst proximate voltage of the distribution power network. For example,the first switch-controlled voltage source may be coupled to any portionof the distribution power network (e.g., a feed line). The firstproximate voltage may be a detected voltage that is proximate to thefirst switch-controlled voltage source. In various embodiments, theprocessor of the first and/or second switch-controlled voltage sourcereceives a voltage value representative of a detected voltage. Theprocessor may monitor the voltage values.

In step 1508, the second switch-controlled voltage source monitors asecond proximate voltage of the distribution power network. For example,the second switch-controlled voltage source may be coupled to anyportion of the distribution power network (e.g., a feed line) at anydistance from the first switch-controlled voltage source. The secondproximate voltage may be a detected voltage that is proximate to thesecond switch-controlled voltage source.

In step 1510, the first switch-controlled voltage source initiates afirst delay duration based on a comparison of the first proximatevoltage to a first set point. The first delay duration may be based onthe first delay value that was generated, received, or preconfigured. Insome embodiments, the first delay duration may be based, at least inpart on any number of delay values. In some embodiments, the firstswitch-controlled voltage source compares the first proximate voltage toany number of set points. If the first proximate voltage is determinedto not be as expected (e.g., too high or too low), the firstswitch-controlled voltage source may initiate a first delay durationbefore engaging in corrective action (e.g., enabling the voltagecompensation component of the first switch-controlled voltage source).

In step 1512, the second switch-controlled voltage source initiates asecond delay duration based on a comparison of the second proximatevoltage to a second set point. The second delay duration may be based onthe second delay value that was generated, received, or preconfigured.In some embodiments, the second delay duration may be based, at least inpart on any number of delay values. In some embodiments, the secondswitch-controlled voltage source compares the second proximate voltageto any number of set points. If the second proximate voltage isdetermined to not be as expected (e.g., too high or too low), the secondswitch-controlled voltage source may initiate a second delay durationbefore engaging in corrective action (e.g., enabling the voltagecompensation component of the first switch-controlled voltage source).

In various embodiments, the first and second switch-controlled voltagesource may monitor the first and second proximate voltage simultaneouslyor near simultaneously. Similarly, both the first and secondswitch-controlled voltage sources may initiate the first and seconddelay durations, respectively, simultaneously or near simultaneously.The delay duration of the first and second switch-controlled voltagesources, however, may be different. As a result, the duration of eitherdelay duration may expire before the other thereby allowing correctiveaction of one of the switch-controlled voltage sources to occur beforethe delay duration of the other switch-controlled voltage sourceexpires.

In step 1514, the second delay duration of the second switch-controlledvoltage source expires before the first delay duration of the firstswitch-controlled voltage source. The processor of the secondswitch-controlled voltage source may determine whether to connect avoltage compensation component of the second switch-controlled voltagesource based on continued monitoring of the second proximate voltage.For example, if the second proximate voltage changes (e.g., is correctedby other switch-controlled voltage sources) and the second proximatevoltage is as expected (e.g., as compared to one or more set points),the processor of the second switch-controlled voltage source maydetermine not to connect or enable the voltage compensation component.If the second proximate voltage is unchanged or still in a range that issufficiently unexpected or undesirable, the second switch-controlledvoltage source may determine to connect the voltage compensationcomponent (e.g., enable one or more capacitors, inductors, or both).

In step 1516, upon determining to connect a voltage compensationcomponent of the second switch-controlled voltage source, the processormay control one or more switches to connect or otherwise enable avoltage compensation component to adjust network voltage. Networkvoltage is a voltage of all or part of a distribution power network. Anetwork voltage component may be all or a part of the voltage or power(e.g., reactive power, real power, or a combination of both).

Those skilled in the art will appreciate that the processor of thesecond switch-controlled voltage source or any processor of anyswitch-controlled voltage source may determine to disable or disconnectthe voltage compensation component based on the determination. Forexample, after the second delay duration expires, the processor of thesecond switch-controlled voltage source may determine to disconnect thevoltage compensation component of the second switch-controlled voltagesource because all or part of the second proximate voltage is too high(e.g., as determined by comparing the monitored second proximate voltageto one or more set points after the expiration of the second delayduration).

In step 1518, the first delay duration of the first switch-controlledvoltage source expires. The processor of the first switch-controlledvoltage source may determine whether to connect a voltage compensationcomponent of the first switch-controlled voltage source based oncontinued monitoring of the first proximate voltage. For example, in amanner similar to that discussed herein regarding the secondswitch-controlled voltage source, if the first proximate voltage changes(e.g., is corrected by other switch-controlled voltage sources) and thefirst proximate voltage is as expected (e.g., as compared to one or moreset points), the processor of the first switch-controlled voltage sourcemay determine not to connect or enable the voltage compensationcomponent. In this example, the first proximate voltage may have changeddue to the action of the second switch-controlled voltage source. If thechanged first proximate voltage is acceptable, the processor of thefirst switch-controlled voltage source may determine not to connect thevoltage compensation component of the first switch-controlled voltagesource. Alternately, if the changed first proximate voltage is stillunacceptable (e.g., the changed first proximate voltage has improved butremains undesirable as compared to one or more set points), theprocessor of the first switch-controlled voltage source may determine toconnect or enable the voltage compensation component to further adjustnetwork voltage.

In step 1520, upon determining not to connect a voltage compensationcomponent of the first switch-controlled voltage source, the firstswitch-controlled voltage source may continue to monitor the firstproximate voltage. The process may continue in step 1506.

Those skilled in the art will appreciate that the processor of the firstswitch-controlled voltage source or any processor of anyswitch-controlled voltage source may determine to disable or disconnectthe voltage compensation component based on the determination. Forexample, after the first delay duration expires, the processor of thefirst switch-controlled voltage source may determine to disconnect thevoltage compensation component of the first switch-controlled voltagesource because all or part of the first proximate voltage is too high(e.g., as determined by comparing the monitored first proximate voltageto one or more set points after the expiration of the first delayduration).

In some embodiments, after one or more operations (e.g., enabling ordisabling a voltage compensation component), any number ofswitch-controlled voltage sources may update one or more delay valuesand/or one or more set points. For example, one or moreswitch-controlled voltage source may lengthen delay durations afterheavy periods of activity to cool one or more switches and/or voltagecompensation components. Further, one or more switch-controlled voltagesource may lengthen delay durations after heavy periods of activity toprolong the life of one or more components such as, for example, one ormore relays.

In some embodiments, after a duration of time with few operations, anynumber of switch-controlled voltage sources may update one or more delayvalues and/or one or more set points. For example, one or moreswitch-controlled voltage source may shorten delay durations after lightperiods of activity to relieve burden from other switch-controlledvoltage sources.

FIG. 16 depicts a block diagram of a pole top voltage source 1602including of a plurality of switch-controlled voltage sources 1608a-1608 n in some embodiments. The pole top voltage source 1602 maycomprise any number of switch-controlled voltage sources. In variousembodiments, the pole top voltage source 1602 is similar to the pole topdevice depicted in FIGS. 11 a-e.

Similar to the discussion regarding FIG. 11 a, in various embodiments,any transformer (e.g., pole top transformer), smart meter, meter, orgrid asset may comprise one or more voltage sources. Each of a pluralityof voltage sources may make determinations and adjust voltageautonomously from others in the pole top transformer. In someembodiments, a plurality of voltage sources may share any number ofcomponents, including, for example, a controller 1604, memory 1606,and/or a power supply unit.

In various embodiments, one or more controllers may control two or moreof the VAR sources in a unit adjacent to or integrated with a pole toptransformer to coordinate voltage adjustment. For example, a singlecontroller may detect proximate voltage, compare the voltage against oneor more set points, determine a voltage adjustment, initiate delaydurations associated with the different voltage sources, and command oneor more of the voltage sources to enable (or disable) a related voltagecompensation component to achieve the desired effect and adjust networkvoltage.

The pole top voltage source 1602 may be coupled with the feeder line1600. In various embodiments, the pole top voltage source 1602 comprisesa processor 1604 (e.g., a controller) coupled to memory 1606 as well asany number of switch-controlled voltage sources 1608 a-n. In variousembodiments, the processor 1604 may generate one or more delay valuesassociated with different switch-controlled voltage source 1608 a-n.

In some embodiments, the pole top voltage source 1602 comprises acommunication interface configured to receive one or more set pointsassociated with one or more switch-controlled voltage sources 1608 a-n.Further, the communication interface may be configured to receive on ormore delays associated with one or more switch-controlled voltagesources 1608 a-n.

The processor 1604 may control the various delays, for example, bychanging the length of a delay value to improve heat dissipation andprolong lifetime of various components (e.g., relays). For example, if asubset of switch-controlled voltage sources has had heavy switching dutyfor a predetermined period of time, the processor 1604 may exclude allor a portion of the subset for a period of time to let the formerlyactive switch-controlled voltage source to cool and prolong the life ofa relay. Similarly, if a subset of switch-controlled voltage source hashad light switching duty for a predetermined period of time, theprocessor 1604 may shorten delays so that the formerly rarely useddevices may perform more switching and allowing other switch-controlledvoltage sources to be used less frequently.

FIG. 17 is a flow chart of a method for controlling a plurality ofswitch-controlled voltage sources 1608 a-n by a processor 1604 in someembodiments. In various embodiments, all or some of theswitch-controlled voltage sources 1608 may be controlled by theprocessor 1604. All or some of the switch-controlled voltage sources1608 a-n may or may comprise separate processors.

In step 1702, the processor 1604 obtains a delay value for each of theswitch-controlled voltage sources 1608 a-n. In some embodiments, theprocessor 1604 utilizes a randomizer to generate one or more of thedelay values. In various embodiments, the processor 1604 may receivedelay values from a centralized communication facility via an optionalcommunication interface or near field communication. Further, theprocessor 1604 may obtain one or more delay values from memory 1606.Those skilled in the art will appreciate that the processor may obtainthe delay values in any number of ways (e.g., generate, receive througha communication interface, or be preconfigured). In another example, thepole top voltage source 1602 may receive a set of delay values toassociate with different switch-controlled voltage sources.

In step 1704, the processor 1604 and/or one of more of theswitch-controlled voltage sources monitor a proximate voltage of thedistribution power network. A proximate voltage is a voltage that isproximate to the pole top voltage source 1602. In step 1706, theprocessor 1604 and/or one of more of the switch-controlled voltagesources compare proximate voltages to at least one set point. The atleast one set point may be, for example, generated, preconfigured, orreceived via the optional communication interface.

In step 1708, if the comparison indicates that the proximate voltage isunexpected or otherwise undesirable, the processor 1604 initiates arespective delay duration for each switch-controlled voltage source 1608a-n. Each different delay duration may be based on a different delayvalue. As a result, different switch-controlled voltage sources 1608 a-nare delaying action based on the associated delay duration.

In step 1710, the processor 1604 determines whether to connect thevoltage compensation component of a switch-controlled voltage source atthe termination of the shortest delay duration. For example, theassociated delay duration for a particular switch-controlled voltagesource may terminate. Upon termination, if the continued monitoring ofthe proximate voltage indicates that the proximate voltage is stillundesirable (e.g., by comparing the proximate voltage to one or more setpoints), the processor 1604 may determine to command the particularswitch-controlled voltage source to engage (or disengage) the associatedvoltage compensation component. If, on the other hand, the proximatevoltage has changed during the delay duration and the proximate voltageis desirable, the processor may not generate any commands to theswitch-controlled voltage sources 1608 a-n.

In step 1712, the processor 1604 may control, based on thedetermination, a switch of the switch-controlled voltage sourceassociated with the shortest delay to connect or couple the associatedvoltage compensation component to adjust network voltage.

Those skilled in the art will appreciate that this process will continuefor each switch-controlled voltage source until the continued monitoringof the proximate voltage indicates that the proximate voltage isdesirable (e.g., by comparing the proximate voltage to one or more setpoints). For example, in step 1714, the processor 1604 determineswhether to connect or couple a voltage compensation component of theswitch-controlled voltage source upon termination of the next shortestdelay duration The determination may be made by comparing the continuedmonitoring of the proximate voltage to one or more set points. Althoughthe continued monitoring of the proximate voltage may, potentially,reflect the adjustments made by the previous switch-controlled voltagesource, the proximate voltage may still be undesirable.

In step 1716, a decision block based on the determination of step 1714results in either controlling a switch of the switch-controlled voltagesource associated with the next shortest delay to adjust network voltagein step 1718, or results in no changes because the proximate voltage iswithin an acceptable range. In some embodiments, if the proximatevoltage becomes acceptable, the processor 1604 may terminate allinitiated delays and not provide any further commands to adjust networkvoltage. In other embodiments, even if the proximate voltage becomesacceptable, separate determinations for each switch-controlled voltagesource may be made based on comparing the proximate voltage to one ormore set points as each delay duration expires.

If a determination is made to enable or disable the voltage compensationcomponent of the switch-controlled voltage source associated with thenext shortest delay duration, the switch of the associatedswitch-controlled voltage source may be controlled to adjust networkvoltage and the process returns to step 1714. The process may continuewhereby the processor 1604 may continue to adjust the network voltage byone or more for the switch-controlled voltage sources at the expirationof each delay duration.

If the processor 1604 determines that further adjustment of the networkvoltage is not necessary (e.g., based on the comparison of the proximatevoltage to one or more set points), the processor 1604 may optionallyselect a subset of switch-controlled voltage source and generatedifferent delay values or, optionally, make a subset of theswitch-controlled voltage source inactive (e.g., unable to make furtherchanges to the network voltage) to allow for heat dissipation and/orextend the life of one or more components. In some embodiments, theprocessor 1604 may adjust delay values for any number ofswitch-controlled voltage sources 1608 a-n to distribute wear, dissipateheat, or the like. The process then continues in step 1704 whereproximate voltage is continued to be monitored and compared to at leastone set point. Those skilled in the art will appreciate that step 1720is optional.

Both FIGS. 18 and 19 depict the voltage response of a feeder to at leastone event where voltage of a substation suddenly changes. FIGS. 18 and19 further display that, in these example, the switch-controlled voltagesources (i.e., nodes) work together due, in part, to the differentdelays of the different switch-controlled voltage source. Since each ofthe switch-controlled voltage sources may delay action for a differentduration before acting to improve network voltage, infighting among thedifferent switch-controlled voltage sources is avoided. As a result,voltage may improve asymptotically (without bouncing back and forthabove and below the desired voltage) thereby steadily approaching thedesired voltage.

FIG. 18 depicts a simulation of voltage performance of nodes (i.e.,switch-controlled voltage sources) on a primary feeder at different timewithout ENVO in some embodiments. Each switch-controlled voltage sourcemay include delays that are different from one or more of the otherswitch-controlled voltage sources. The horizontal axis refers to time inseconds while the left vertical axis refers to network voltage. Theright vertical axis refers to switched-in capacity kVar. Although thehorizontal axis refers to time in seconds, those skilled in the art willappreciate that time may be in any increment including, but not limitedto, nanoseconds, cycles, or partial cycles. Similarly, although theright axis refers to kVar, the voltage compensation components of theswitch-controlled voltage sources may compensate for real power,reactive power, or both.

System startup refers to startup of the simulation. The simulationbegins around time 2.8 seconds along the horizontal axis. The dottedline at approximately 2.8 seconds refers to the initiation of thesimulation. At time 4 seconds, the substation drops voltage fromapproximately 1.01 to approximately 0.99. The multiple nodes 3, 5, 7, 9,11, and 13 respond within fractions of a second to improve the voltageto approximately 0.9998. Thereafter, minor improvements are made afterdifferent delays by one or more of the switch-controlled voltage sourcethat goes from a broad band from approximately 4.3 seconds to 5.5seconds to an improved narrow band at approximately 5.5 seconds to theend of the simulation at 8 seconds.

The switched-in cap dotted line represents the amount of capacitydelivered by the different voltage compensation components of thedifferent switch-controlled voltage sources. Until approximately thedrop of voltage of the substation, the total capacity provided by allnodes is approximately 110 kVar. As more of the nodes engage theirassociated voltage compensation components, the total capacity inputinto the system from the nodes increases to approximately 200 kVar(without ENVO).

Those skilled in the art will appreciate that, by implementing delaysbefore acting, each switch-controlled voltage source can constantlymonitor and potentially make adjustments to network voltage with littleto not infighting. As a result of multiple nodes operating in concert,without relying on external control or communication between nodes, theoverall voltage of the feeder is quickly and efficiently improved.

FIG. 19 depicts a simulation of voltage performance of nodes on aprimary feeder at different time with ENVO in some embodiments. Asdiscussed regarding FIG. 18, each switch-controlled voltage source mayinclude delays that are different from one or more of the otherswitch-controlled voltage sources. The horizontal axis refers to time inseconds while the left vertical axis refers to network voltage. Theright vertical axis refers to switched-in capacity kVar. Although thehorizontal axis refers to time in seconds, those skilled in the art willappreciate that time may be in any increment including, but not limitedto, nanoseconds, cycles, or partial cycles. Similarly, although theright axis refers to kVar, the voltage compensation components of theswitch-controlled voltage sources may compensate for real power,reactive power, or both.

System startup refers to startup of the simulation. The simulationbegins around time 1.9 seconds along the horizontal axis. The dottedline at approximately 1.9 seconds refers to the initiation of thesimulation. At time 4 seconds, there is a load change (i.e., a load stepincrease). Multiple nodes 3, 5, 7, 9, 11, and 13 respond withinfractions of a second to improve the voltage. Thereafter, minorimprovements are made after different delays by one or more of theswitch-controlled voltage source that goes from a broad band fromapproximately 4.3 seconds to 5.9 seconds to an improved narrow band atapproximately 5.9 seconds to the end of the simulation at 8 seconds.

The switched-in cap dotted line represents the amount of capacitydelivered by the different voltage compensation components of thedifferent switch-controlled voltage sources. Until approximately thedrop of voltage of the substation, the total capacity provided by allnodes is approximately 90 kVar. As more of the nodes engage theirassociated voltage compensation components, the total capacity inputinto the system from the nodes increases to approximately 160 kVar (withENVO).

In some embodiments, one or more of the nodes 3, 5, 7, 9, 11, and 13include the n-cycle delay control 1402 and the slow/fast integralcontrol module 1404 of FIG. 14. In some embodiments, the portions of thedepictions in FIGS. 18 and 19 that shows the greatest change (e.g.,approximately between 4 seconds and 4.2 seconds) may be the response ofthe n-cycle delay control module 1402 of each respective node. Theimproved broad response may include responses of a combination of then-cycle delay control module 1402 of some nodes and the responses of theslow/fast integral control 1404 of other nodes. The narrow band mayinclude, for example, responses from the slow/fast integral control 1404of other nodes.

FIG. 20 depicts a control approach by an aggregated controller perswitch-controlled voltage sources where variable Q (e.g., adjustedvoltage such as, for example, kVAR) is injected over a fixed timeinterval until convergence occurs in some embodiments. In someembodiments, there may be an aggregated controller per switch-controlledvoltage source, be it a 10-kVAR or an 80-kVAR switch-controlled voltagesource. For example, a pole top system may comprise one controller thatcontrols multiple different switch-controlled voltage sources (e.g., seeFIGS. 11 a-e). Such an approach may eliminate undesired interactionbetween the control loops for each individual switched switch-controlledvoltage source, as a single ‘loop’ may be determine how many totalcapacitors to switch online at any given time.

In this example, variable Q is injected over a pre-determined fixed timeinterval. In some embodiments, the amount of Q to be injected at anytime step is determined by the square of the voltage error. In oneexample, this behavior is expressed by

ΔQ=Δt·K _(QT) ·|V*−V| ²,  (1)

where Δt is the fixed time step when a switching action can take placeand K_(QT) is a gain value that scales the amount of Q to be injectedbased on system characteristics, speed of response desired, and todecouple controller interactions of two adjacent switch-controlledvoltage sources.

FIG. 21 depicts a simulation of a load voltage response to an inputvoltage step decrease in some embodiments. In FIG. 21, the input voltagedrops at approximately 0.2 seconds. At approximately 0.21 seconds, oneor more of the switch-controlled voltage sources respond to adjustnetwork voltage with variable Q at fixed time intervals. In thisexample, the total voltage raises to approximately 0.99 by approximatelytime 0.24 seconds and then is maintained. The simulation ends atapproximately 0.4 seconds.

FIG. 22 depicts a simulation of a load voltage response to a load stepincrease in some embodiments. In FIG. 22, there is a load step increaseat approximately 0.2 seconds. At approximately 0.22 seconds, one or moreof the switch-controlled voltage sources respond to adjust networkvoltage with variable Q at fixed time intervals. Like the previousexample, the total voltage raises to approximately 0.99 by approximatelytime 0.23 seconds and then is maintained. The simulation ends atapproximately 0.4 seconds.

It may be noted between the two simulations of FIGS. 21 and 22 that thetotal switched-in capacity of the one or more nodes may be less whenresponding to a load step increase as opposed to responding to an inputvoltage step decrease.

FIG. 23 depicts a control approach by an aggregated controller perswitch-controlled voltage sources where fixed Q (e.g., adjusted voltagesuch as, for example, kVAR) is injected over a variable time interval insome embodiments. In various embodiments, delta Q (i.e., the amount ofreactive power, real power, or both provided by one or more of theswitch-controlled voltage sources) is fixed, while the injection timeinterval is varied. This approach may eliminate large voltage swing. Forexample, this approach may eliminate a large voltage swing when a largeamount of VAR is suddenly injected. However, convergence may occur moreslowly. The variable time may be calculated based on:

$\begin{matrix}{{\Delta \; t} = {K_{T}/{{{V^{*} - V}}.}}} & (2)\end{matrix}$

This time may be continuously updated, as changes in load, sources, andinjection level of adjacent VAR unit may change the grid voltage. Invarious embodiments, the closer the voltage is to the reference value,the longer the time between the next interval until the limit of theabove expression equals infinity when V is equal to V*.

FIG. 24 depicts a simulation of a load voltage response to an inputvoltage step decrease in some embodiments. In FIG. 24, the simulationbegins at approximately 2.9 seconds and the input voltage of asubstation drops from approximately 1.01 to 0.99 at approximately 4seconds. At fractions of a second, one or more of the switch-controlledvoltage sources respond to adjust network voltage with fixed Q atvariable time intervals. In this example, the total voltage raises toapproximately 0.9999 by approximately time 6.2 seconds and then ismaintained. The simulation ends at approximately 8 seconds.

As discussed herein, the network voltage adjustment with the fixed Q atvariable time intervals reduces large voltage swings and smoothes outthe response curve of the multiple nodes. As a result, it may be longer(e.g., fractions of a second) before the desired voltage is reached.

FIG. 25 depicts a simulation of a load voltage response to a load stepincrease in some embodiments. In FIG. 25, simulation begins atapproximately 2.4 seconds and the load step increases at approximately 4seconds. At fractions of a second, one or more of the switch-controlledvoltage sources respond to adjust network voltage with fixed Q atvariable time intervals. In this example, the total voltage raises toapproximately 0.9999 by approximately time 6.9 seconds and then ismaintained. The simulation ends at approximately 8 seconds.

It may be noted between the two simulations of FIGS. 24 and 25 that thetotal switched-in capacity of the one or more nodes may be less whenresponding to a change in input voltage as opposed to responding to aload step increase.

The operation of non-linear loads in a power distribution system createsharmonic currents that flow throughout the power system. Inductivereactance of the power system increases and capacitive reactancedecreases as harmonic order increases. At a given harmonic frequencythere will be a crossover point where inductive and capacitivereactances are equal. The crossover point is where the powerdistribution system has coincidental similarity with system impedances.When source harmonics exist at a frequency where the impedances match orare sufficiently similar, harmonic resonance may result in very highharmonic currents and voltages. In one example, when a capacitor orgroup of capacitors of a power distribution system have the samereactance at a frequency equal to one of the characteristic frequenciescreated by the loads, harmonic resonance may result.

In the prior art, due to the changing nature of loads in a powerdistribution system, harmonic resonance is typically ignored unlessproblems in the system require corrective action. For example, extracapacitance reactance may be added to the power distribution systemwithout regard to possible harmonic resonance. Resulting harmonicresonance may lead to undesirable results such as erratic behavior orelectrical control equipment, opening of capacitor fuses, capacitorfailure, source transformer failure, or the like

The operation of non-linear loads in a power distribution system maycreate harmonic currents that flow throughout the power system.Inductive reactance of the power system increases and capacitivereactance decreases as harmonic order increases. At a given harmonicfrequency there will be a crossover point where inductive and capacitivereactances are equal. The crossover point is where the powerdistribution system has coincidental similarity with system impedances.When source harmonics exist at a frequency where the impedances match orare sufficiently similar, harmonic resonance may cause very highharmonic currents and voltages. In one example, when a capacitor orgroup of capacitors of a power distribution system have the samereactance at a frequency equal to one of the characteristic frequenciescreated by the loads, harmonic resonance may result.

In the prior art, due to the changing nature of loads in a powerdistribution system, harmonic resonance is typically ignored unlessproblems in the system require corrective action. For example, extracapacitance reactance may be added to the power distribution systemwithout regard to possible harmonic resonance. Resulting harmonicresonance may lead to undesirable results such as erratic behavior ofelectrical control equipment, opening of capacitor fuses, capacitorfailure, source transformer failure, or the like.

Unfortunately, systems that add or reduce capacitance, such as thosethat engage and disengage VAR compensation components, may cause inharmonic resonance. Harmonic resonance may be triggered by changes incapacitance such as when one or more capacitors are switched on or off.For example, without any corrective measures, assuming a sourceimpedance at a bus of 250 MVA and a capacitor bank (e.g., associatedwith one or more VAR sources discussed herein), rating of 10 MVA, thecapacitor bank will resonate with the source impedance at the 5^(th)harmonic:

${{harmonic}\mspace{14mu} {{resonance}({hR})}} = \sqrt{\frac{250}{10} = 5.00}$

where:

${{harmonic}\mspace{14mu} {resonance}\mspace{14mu} ({hR})} = \sqrt{\frac{M\; V\; A_{sc}}{M\; V\; A\; R_{cap}}}$

(a harmonic order may be estimated as MVA_(sc) of the source impedanceat the MVAR_(cap) is the 3-phase rating in MVA of the capacitor bank).

Accordingly, a challenge for a fast VAR source, such as someembodiments, described herein, is likely to be the question of harmonicsource and sink resonances. Most capacitors deployed on the grid do notfeature any level of harmonic isolation. In the past, where gridtopology did not change, and when harmonic sources were not prevalent onthe grid, this may have been adequate. However, as variable levels ofcapacitance (and inductance) are deployed in one or more fast VARsources, source-sink resonant frequencies may widely shift, raising thepossibility that a resonance condition is excited with a nearby ordistant source.

FIG. 26 is a circuit diagram of an exemplary switch-controlled VARsource 2600 including a harmonic management block (HMB) 2606 in someembodiments. The switch-controlled VAR source 2600 may be a part of alarge number of switch-controlled VAR sources 2600 at or near an edge ofthe power distribution grid (i.e., the power network). Although theswitch-controlled VAR source 2600 is depicted as including a singlecapacitor as a VAR compensation component, there may be any number ofcapacitors and/or inductors that may be individually controlled by thecontroller 2618. Examples may include, but are not limited to, pole topembodiments depicted in FIGS. 11 a-e, 16, 17, 33, and 34 as well as therelated description herein.

Similar to the switch-controlled VAR source 400, the switch-controlledVAR source 2600 comprises a capacitor 2608 (e.g., a VAR compensationcomponent) that is controlled through a relay 2610 in parallel with asemiconductor switch 2612 (e.g., triac 2616—NTC 2614 is optional). Aprocessor, such as controller 2618, may control the relay 2610 andsemiconductor switch 2612 based on voltage. The components of theswitch-controlled VAR source 2600 that are similar to theswitch-controlled VAR source 400 may perform similar functions in asimilar way.

As discussed herein, the engagement or disengagement of one or morecapacitors and/or inductors by the switch-controlled VAR source 2600 mayresult in harmonic resonance. Harmonic resonance may be difficult topredict and model because of the complex nature and changing number ofloads in any given portion of a power distribution grid. In variousembodiments, the HMB 2606 is configured to detect increased voltage thatis a result of resonance and provide or assist in providing correctiveaction to shift, isolate, alter, or eliminate the resonance.

The HMB 2606 comprises a resonance detection module which may comprise acomparator, for example, that, when the voltage is compared to aresonance threshold, may cause or assist in causing an engagement ordisengagement of a resonance compensation component. In variousembodiments, the HMB 2606 may shift, isolate, alter, or eliminate theresonance in any number of ways. In one example, the HMB 2606 comprisesa resonance compensation component that is engaged when resonance isdetected. The resonance compensation component may include or beconfigured to add resistance, add capacitance, subtract capacitance, addinductance, subtract inductance to the network. The HMB 2606 may isolateharmonic resonance. Examples of HMB 2606 include, but are not limitedto, depictions in FIGS. 27, 29, and 31.

In various embodiments, the HMB 2606 assists in or directly enables,engages, or disengages one or more resonance compensation components ifvoltage proximate to the switch-controlled VAR source 2600 is greaterthan a resonance threshold. As a result, harmonic resonance, potentiallycontributed by VAR compensation components of the switch-controlled VARsource 2600, may be isolated, shifted, altered, or eliminated. The HMB2606 may comprise a processor, utilize the controller 2618, or functionwithout a processor.

One or more of the plurality of switch-controlled VAR source 2600coupled to the power network may include the HMB 2606. In one example,an HMB 2606 may be within every switch-controlled VAR source 2600. Insome embodiments, the HMB 2606 may be separate from theswitch-controlled VAR source 2600.

Like the exemplary switch-controlled VAR source 400, exemplaryswitch-controlled VAR source 2606 comprises lines 2602 and 2626, fuse2604, resistors 2620 and 2622, capacitor 2608, relay 2610, a switch 2612comprising an optional NTC 2614 and triac 2616, controller 2618, andpower supply unit (PSU) 2624.

Lines 2602 and 2626 may be coupled to a feeder such as a feeder on thelow voltage side of a transformer. In one example, lines 2602 and 2626may be coupled to any line or feeder configured to provide power to oneor more loads (e.g., on or at the edge of a network).

The HMB 2606 may be within or independent of the switch-controlled VARsource 2600. In some embodiments, the switch-controlled VAR source 2600and/or the HMB 2606 is proximate to a residential or commercial load.For example, the switch-controlled VAR source 2602 and/or the HMB 2606may be within a smart meter, ordinary meter, or transformer withinproximity to a load. Those skilled in the art will appreciate that theswitch-controlled VAR source 2602 and/or the HMB 2606 may be within anygrid asset.

The fuse 2604 is configured to protect the switch-controlled VAR source2600 and/or the HMB 2606 from voltage spikes, transients, excessivecurrent, or the like. The fuse 2604 may prevent excessive thermalloading of a failed component, thus allowing the grid to operate even asthe VAR source is removed from the circuit. The fuse 2604 may be anyfuse and may be easily replaceable. In some embodiments, there are aplurality of HMB 2606 located within the power grid, each of the HMB2606 being coupled to a different fuse 2604. In one example, if the fuse2604 clears and the switch-controlled VAR source 2600 and/or the HMB2606 is disconnected from the power distribution network, the powerdelivered to the residential and/or commercial loads may not beinterrupted.

One difference as depicted between the switch-controlled VAR source 400and the switch-controlled VAR source 2600 is the optional inductor 406and resistor 408 as depicted in FIG. 4 a. Although not depicted in FIG.26, the switch-controlled VAR source 2600 may comprise the optionalinductor 406 and resistor 408 which may act as an L-R snubber to controlpeak inrush currents (e.g., during startup conditions) and to manageharmonic resonances. Those skilled in the art will appreciate that, insome embodiments, the inductor 406 and resistor 408 may reducesusceptibility of the capacitor 2610 to harmonic resonance. Further, theswitch-controlled VAR source 2600 may comprise the optional bleedresistor 410 (see FIG. 4 a)

The capacitor 2608 may be any capacitor configured to compensate forreactive power (e.g., VARs). In various embodiments, the relay 2610and/or the semiconductor switch 2616 may form a switch that completesthe circuit thereby allowing the capacitor 2608 to influence reactivepower of the network. As discussed regarding FIG. 4 a, in one example,if the relay 2610 is open and the triac 2616 (of the semiconductorswitch 2612) is deactivated, the capacitor 2608 may be a part of an opencircuit may, therefore, have no effect on the power distribution gird orthe load.

The relay 2610 may be used to reduce losses when the semiconductorswitch 2612 is active. The semiconductor switch 2612 may be used toprovide precise and fast response at turn on and turn off. Those skilledin the art will appreciate that any appropriately rated relay (e.g., atested electromechanical relay) may be used. The triac 2616 of thesemiconductor switch 2612 may be a gate-controlled thyristor in whichcurrent is able to flow in both directions. The relay 2610 and/or thetriac 2616 may perform as one or more switches. As similarly discussedwith regard to FIG. 4 a, those skilled in the art will appreciate thatany switch may be used. For example, a switch S, such as an IGBT,thyristor pair, or thyristor/diode arrangement may also be used. Inanother example, a mosfet or IGBT may be used with a diode in parallelto control the capacitor 2608.

Resistors 2620 and 2622 may attenuate the signal from the line 2602 tobe received by the controller 2618.

The controller 2618 may be configured to determine a proximate voltagebased on the voltage of line 2602 and may enable or disable thecapacitor 2608. In various embodiments, the controller 2618 is aprocessor such as a microprocessor and/or a Peripheral InterfaceController (PIC) microcontroller may detect voltage of the feeder 2602.In some embodiments, the controller 2618 may receive an indication thata voltage sensed by the HMB 2606 is greater than a resonance threshold.Based on the indication, the controller 2618 may direct the HMB 2606 toenable or engage a resonance compensation component or, in someembodiments, the controller 2618 may disengage the capacitor 2608 (e.g.,by opening relay 2610 and deactivating triac 2616).

The controller 2618 may control the relay 2610 and/or the triac 2616 toopen or close the circuit thereby enabling or disabling the capacitor2610. For example, if detected proximate voltage is not desirable, thecontroller 2610 may enable the capacitor 2608 by commanding the triac2616 to activate and/or the relay 2610 to close. The capacitor 2608 maythen compensate for reactive power (e.g., regulate network voltage). Inanother example, if proximate voltage is greater than a resonancethreshold, the controller 2618 may be configured to deactivate the triac2616 and open the relay 2610 to disengage the capacitor 2608. In thisexample, disengagement of the capacitor 2608 may be considered asactivating or engaging a resonance compensation component to alter oreliminate resonance.

Those skilled in the art will appreciate that there may be a delay inthe response of relay 2610 (e.g., the relay 2610 may be anelectromechanical relay that is slow to react when compared to the triac2616). In this example, the command to open the relay 2610 may be sentin advance of the command to deactivate the triac 2616. In someembodiments, a command may be sent to turn off the relay 414.Subsequently, after a time delay, the triac 420 may be turned off.Similarly, there may be a delay (at a same or different duration thanthe delay previously discussed) in engaging or disengaging one or moreresonance compensation components (e.g., either by the processor orconfigured in solid state circuitry).

The controller 2618 may delay activation or deactivate the switch (e.g.,relay 2610 and semiconductor switch 2616). In various embodiments, amultitude of switch-controlled VAR sources 2600 which react to voltageswithin a power grid. In order to prevent infighting among theswitch-controlled VAR sources 2600, one or more of the devices may delayenabling or disabling the VAR compensation component (e.g., capacitor2608). In various embodiments, the controller of each switch-controlledVAR source 2600 includes a different delay. As a result, eachswitch-controlled VAR source 2600 may activate the switch to regulatevoltage at a different time thereby giving each device time to detectvoltage changes that may result from one or more switch-controlled VARsources 2600.

The power supply unit (PSU) 2624 may adapt the power to be suitable tothe controller 2618. In some embodiments, the controller 2624 issupplied from power supplied by the line 2602, batteries, or any otherpower source. The PSU 2624 may be any power supply.

In various embodiments, the switch-controlled VAR source 2600 mayoperate both dynamically and autonomously to regulate voltage and/orcompensate for grid faults. Those skilled in the art will appreciatethat the switch-controlled VAR source 2600 may adjust reactive power andthus the network voltage based on detected voltage without detecting oranalyzing current. In some embodiments, load current information can bederived from an additional current sensor, or from the smart meter.

In some embodiments, the switch-controlled VAR source 2600 may comprisean inductor which may be used to adjust voltage. For example, one ormore inductors may be in place of capacitor 2608. In another example,one or more inductors may be in parallel with the capacitor 2608. Theinductor(s) may be coupled to the fuse 2604 (or a different fuse) andmay be further coupled to a separate switch. For example, theinductor(s) may be coupled to a relay in parallel with a triac (ormosfet or IGBT) which may perform switching similar to the relay 2610and the semiconductor switch 2612. The controller 2618 may enable theinductor and disable the capacitor 2608 by enabling one switch andcreating an open circuit with the other. Similarly, the controller 2618may disable the inductor and enable the capacitor 2608 or, alternately,disable both. Those skilled in the art will appreciate that the triacassociated with the inductor may also be coupled to an NTC resistor toallow the triac to be activated at any time.

The switch-controlled VAR source 2600 may be switch-controlled to thepower distribution grid. In one example, the switch-controlled VARsource 2600 is coupled in shunt via conductive lines 2602 and 2626 at orproximate to a residence or other commercial load. A shunt connectionmay be the connection of components within a circuit in a manner thatthere are multiple paths among which the current is divided, while allthe components have the same applied voltage.

In one example, a feed line may extend from a transformer to one or moreloads (e.g., residences). The feeder may also be coupled with aswitch-controlled VAR source 2600 in shunt. In some embodiments, if theswitch-controlled VAR source 2600 fails or was otherwise inoperative,the delivery of power by the power distribution grid is not interruptedbecause of the shunt connection (e.g., even if the connection to theswitch-controlled VAR source 2600 became an open circuit, there may beno interruption of power between the transformer and the one or moreloads along the feed line).

In various embodiments, the switch-controlled VAR source 2600 and/or theHMB 2606 may be collocated inside or with a utility meter (e.g., smartmeter), so that installation can be piggybacked, saving the utility intotal installation and reading costs. The switch-controlled VAR source2600 may leverage a communication link inside a smart meter tocommunicate with the utility, take VAR dispatch or voltage set-pointcommands, take resonance threshold(s), and/or inform the utility ofmalfunction. Multiple switch-controlled VAR sources 2600 may becollocated in a common housing and can be mounted on another grid asset,such as a pole-top or pad-mount transformer. This may allow lower costVAR compensation, reduce the cost of a communication link, and allowadditional value to be derived, such as assessing status and lifeexpectancy of the asset.

In various embodiments, a plurality of switch-controlled VAR sources mayeach comprise a communication module. A communication module is anyhardware configured to communicate wirelessly or by wire with one ormore digital devices or other switch-controlled, switch-controlled VARsources. The communication module may comprise a modem and/or anantenna.

One or more of the switch-controlled VAR sources 2600 may receive one ormore set points with which to compare against voltage to assist in thedetermination to engage the VAR compensation component. A set point maybe a predetermined value to improve voltage regulation. The processor ofswitch-controlled VAR source may determine whether to adjust voltagebased on the comparison of the proximate voltage to the set points.Those skilled in the art will appreciate that the set points may bedifferent for different switch-controlled VAR sources.

For example, the switch-controlled VAR source may compare detectedvoltage of a feeder (e.g., proximate voltage) to one or more set pointsto make the determination of whether to activate the capacitor based onthe comparison. For example, if the detected voltage is lower than apreviously received set point, the switch-controlled VAR source mayenable the capacitor to increase voltage. Alternately, if the voltage ishigher than a previously received set point, the switch-controlled VARsource may disable an otherwise active capacitor in order to reducevoltage.

Similarly, one or more of the switch-controlled VAR sources 2600 mayreceive one or more resonance thresholds with which to compare againstvoltage to assist in the determination to engage the resonancecompensation component. A resonance threshold may be a predeterminedvalue to shift, isolate, alter, or eliminate resonance. The processor ofswitch-controlled VAR source 2600 may determine whether to adjustvoltage based on the comparison of a first or second proximate voltageto the resonance threshold(s). Those skilled in the art will appreciatethat the resonance threshold(s) may be different for differentswitch-controlled VAR sources.

In some embodiments, a communication facility may dispatch and/or updateone or more set points and/or one or more resonance thresholds. Theswitch-controlled VAR sources may communicate via a cellular network,power line carrier network (e.g., via the power grid), wirelessly, vianear-field communications technology, or the like. The communicationfacility may update set points of any number of switch-controlled VARsources at any rate or speed. For example, the communication facilitymay update set points based on changes to the grid, power usage, or anyother factors.

In some embodiments, one or more of the switch-controlled VAR sourcesmay both receive and provide information. For example, one or more ofthe switch-controlled VAR sources may provide VARs provided, devicestatus, voltage information, current information, harmonic information,and/or any other information to one or more communications facilities(e.g., digital devices).

The information detected, received, or otherwise processed by one ormore of the switch-controlled VAR sources 2600 may be tracked andassessed. For example, voltage and/or other power information may betracked by the VAR source or a centralized facility to determine usagerates and identify inconsistent usage. The energy usage at anaggregation point, such as at a transformer where the VAR source islocated, may be compared with usage recorded by all the meters connecteddownstream to identify potential energy theft. A history of expectedusage may be developed and compared to updated information to identifychanges that may indicate theft, failure of one or more grid components,or deteriorating equipment. In some embodiments, one or moreswitch-controlled VAR sources 2600 may provide information to monitoraging equipment. When changes to voltage or other information indicatesdeterioration or degradation, changes, updates, or maintenance may beplanned and executed in advance of failure.

Those skilled in the art will appreciate that the controller of theswitch-controlled VAR source 2600 may enable or disable an inductor. Insome embodiments, as discussed herein, the switch-controlled VAR source2600 may comprise an inductor and a capacitor in parallel. In someexamples, based on the comparison of the detected voltage to one or morereceived set points, the controller of the switch-controlled,switch-controlled VAR source 2600 may enable or disable the inductor andthe capacitor independently.

In various embodiments, a resistor and/or an NTC may be in series withthe relay 2610 which may further protect the circuit and/or extend thelife of the relay 2610. For example, a second NTC in series with therelay may prevent current inrush. As a result, the second NTC mayprevent contact erosion and life degradation for the relay.

In various embodiments, like the switch-controlled VAR source 400 asdiscussed with regard to FIG. 4, different HMB 2606 devices may belocated at a plurality of positions at or near the edge of a network.The different HMB 2606 may each act independently, however, in theaggregate, the effect may shift, isolate, alter, or eliminate harmonicresonance at multiple points or throughout a power network.

In some embodiments, one or more of a set of HMB 2606 units may comprisedifferent resonance thresholds whereby the units only assist or directlyengage one or more resonance compensation components at differentdetected voltages. In another example, a separate processor (e.g., partof the switch-controlled VAR source 2600) or a processor within the HMB2606 is configured to directly or assist in enabling or engaging one ormore resonance compensation components.

FIGS. 27, 29, and 31 depict different circuits for the HMB. Thesefigures and the associated description are non-limiting examples. Thereare many different circuits and methods for the HMB that are apparentfrom the descriptions herein.

FIG. 27 is a diagram of an HMB 2700 that is configured to add a resistor2720 when a voltage is greater than a resonance threshold in someembodiments. For example, the HMB 2700 may function as a harmonicdampening block whereas the resistor 2720 may be engaged to dampenresonance. The HMB 2700 comprises a line 2702, an inductor 2704, a diodebridge (i.e., diodes 2706, 2708, 2710, and 2712), diode 2714, resistors2716, 2718, and 2720, and switch 2722. In some embodiments, the HMB 2700comprises a resonance detection module and a resonance compensationcomponent. The resonance detection module, for example, may comprise,but not be limited to, the inductor 2704 and the diode 2714 forcomparing voltage to a resonance threshold. The resonance compensationcomponent may comprise, but not be limited to, the resistor 2720.

In various embodiments, the HMB 2700 receives voltage from line 2702across inductor 2704. The optional diode bridge (i.e., diodes 2706,2708, 2710, and 2712) may convert the voltage from AC to DC. Theresistors 2716 and 2718 may be an optional voltage divider. When the DCvoltage is greater than a set point of the diode 2714, the switch 2722may be engaged thereby enabling resistor 2720 (e.g., enabling theresistor 2720 to be added to the circuit thereby altering or eliminatingresonance). The diode 2714 may be any kind of diode including, forexample, a zener diode.

In one example, the inductor 2704 serves to amply the higher frequencycomponent because the voltage drop across the inductor 2704 may beapproximated by V=w*L*i, where w is the harmonic frequency. As a result,the current component of the higher harmonic may have a larger voltagedrop across the inductor 2704. A relatively large amplitude harmoniccurrent may have a large voltage drop which may break down the diode2714 (e.g., a zener diode). As a result, the switch 2722 activates andthe resistor 2720 dampens the harmonic (e.g., the resistor 2720 dampensthe energy present in voltage peaks).

Those skilled in the art will appreciate that the quality and propertiesof the components of the HMB 2700 may be chosen such that when thevoltage across the inductor 2704 is above a resonance threshold (i.e.,the break down voltage of zener diode 2714) or the divided, DCrepresentation of the voltage across the inductor 2704 is above theresonance threshold, the resistor 2720 is engaged in the circuit. Theresistor 2720 may be of any size to dampen the harmonic resonance.

The switch 2722 may be any transistor controlled by the diode 2714.

In various embodiments, there may be any number of resistors to alter oreliminate the harmonic resonance. For example, the HMB 2700 may beconfigured to engage any number of resistors when voltage of atransmission line is greater than one or more resonance thresholds.

FIG. 28 is a flowchart for altering or eliminating resonance utilizingHMB 2700 (see FIG. 27) within the switch-controlled VAR source 2600 (seeFIG. 26) in some embodiments. In step 2802, the switch-controlled VARsource 2600 detects a first proximate voltage at a point in the path(e.g., at a point in a power distribution network). In step 2804, theswitch-controlled VAR source 2600 compares the first proximate voltageto a voltage threshold. In step 2806, the switch-controlled VAR source2600 determines to enable a VAR compensation component based oncomparison to compensate for VAR in path. This process may be analogousto other processes described herein (e.g., see FIG. 6).

In step 2808, the HMB 2700 detects a second proximate voltage. In oneexample, a voltage across inductor 2704 is received by the HMB 2700.Line 2702, coupled to inductor 2704, may be coupled to the same or asimilar position to the point in the path from which the first proximatevoltage was detected.

In optional step 2810, the HMB 2700 converts at least a portion of thesecond proximate voltage to DC utilizing the diode bridge (e.g., diodes2706, 2708, 2710, and 2712).

In step 2812, the HMB 2700 detects if the DC second proximate voltage isgreater than a resonance threshold. In various embodiments, if the DCsecond proximate voltage is greater than a break down voltage of thezener diode 2714, the DC second proximate voltage is greater than theresonance threshold. In this example, the resonance threshold isgenerally equal to the zener diode 2714 break down voltage. In someembodiments, the DC proximate voltage is subject to a voltage divider(e.g., resistors 2716 and 2718).

In step 2814, the damping resistor 2720 is engaged with the path 2702 toalter or eliminate harmonic resonance based on the DC second proximatevoltage being greater than the resonance threshold. In some embodiments,once the second DC proximate voltage is greater than the resonancethreshold, the transistor 2722 is closed or engaged, thereby engagingresistor 2720 within the circuit. In one example, the resistor 2720 isengaged to be in parallel with inductor 2704 which may dampen resonance.

FIG. 29 is a diagram of an HMB 2900 that is configured to isolateresonance when voltage is greater than at least one resonance thresholdin some embodiments. The HMB 2900 may function as a harmonic isolationblock whereas an inverter synthesizes harmonic voltages in anti-phase tocancel harmonics. For example, the HMB 2900 may utilize an inverter toinject harmonic voltages in anti-phase with the previously detectedharmonics so that the harmonic is at least partially cancelled toprevent the harmonic (or a portion of the harmonic) from being imposedacross a VAR compensation component of a switch-controlled VAR source.

The HMB 2900 comprises a transformer, capacitors 2908, 2924, and 2926,inductor 2910, and two switches. The transformer comprises a primarywinding 2904 (N1) and secondary winding 2906 (N2). The first switchcomprises diode 2912 and transistor 2916 which may be controlled, atleast in part, through line 2920 which may be coupled to the transistor2916. The second switch comprises diode 2914 and transistor 2918 whichmay be controlled, at least in part, through line 2922 which may becoupled to the transistor 2918.

In some embodiments, the HMB 2900 comprises a resonance detection moduleand a resonance compensation component. The resonance detection module,for example, may comprise, but not be limited to, the transformer andswitches for comparing voltage to a resonance threshold. The resonancecompensation component may comprise, but not be limited to, thecapacitors 2924 and 2926. The capacitors 2924 and 2926 may act as DCvoltage sources and the two switches may invert the DC voltages tosynthesize harmonic voltages in anti-phase with what is present on thegrid. As a result, the harmonics may cancel. Subsequently, theswitch-controlled VAR source may “see” the fundamental component of theline and not the harmonics. The HMB 2900 isolates the main VARcompensation components of a VAR source from harmonics on the grid. Insome embodiments, the HMB 2900 partially cancels the harmonics.

In various embodiments, the HMB function is performed utilizing aninverter comprising transistors 2916 and 2918. In some embodiments, aseries connected transformer of windings 2904 and 2906 is coupled to asmall rated inverter on the higher voltage side. For instance, thetransformer may be required to block 5% of 5^(th) harmonic voltage (300hertz for a 60 hertz system) on a 277 volt nominal ac voltage. Thiswould correspond to about 14 volts, a small rating relative to the 277volt nominal value of the fast VAR source. In one example, the seriestransformer could step up the voltage to 280 volts, dropping the linecurrent by a factor of 20, reducing the rating of the inverter by asimilar factor. Several methods are known for the control of such activefilters, including the use of synchronous frame controllers, or the useof resonant controllers. The HMB 2900 active filter operation may alsoinclude dc voltage bus control. The HMB 2900 may be configured aroundmultiple inductive or capacitive elements of a switch-controlled VARsource or could be used to compensate for an entire block of VARcompensation components of one or more switch-controlled voltagesources, without loss of generality or principle.

In various embodiments, lines 2920 and 2922 may control the resonancethreshold for the transistors 2916 and 2918. For example, lines 2920 and2922 may be coupled to one or more processors (e.g., controller 2618 ofthe switch-controlled voltage source 2600 of FIG. 26). The processor maybe configured to set the resonance threshold(s) by biasing thetransistors 2916 and/or 2918. In some embodiments, there is no processorbut rather the resonance thresholds are maintained in memory or solidstate circuitry.

In some embodiments, the processor may be configured (e.g., via acommunication module or during installation) with a first resonancethreshold and a second resonance threshold. The processor may biastransistor 2916 via line 2920.

In various embodiments, once harmonics are detected (e.g., the voltagefrom the transformer closes the biased switch(es)), the HMB 2900 maysynthesize anti-phase harmonic voltages. The process may continue untilthe harmonic present is in excess of the rating of the HMB 2900 at whichpoint the HMB 2900 may compensate as possible. The remaininguncompensated resonance (which is likely greatly reduced) may, in someembodiments, pass through to the switch-controlled VAR source. Invarious embodiments, if the uncompensated resonance is too great, thecontroller 2618 (see FIG. 26) of the switch-controlled VAR source 2600may enable or disable capacitors and/or inductors to detune gridharmonics.

In various embodiments, the transistors 2916 and 2918 have differentproperties (e.g., the transistors are part of a CMOS device) therebyallowing engagement at different voltages from the transformer.

In various embodiments, the HMB 2900 may be further configured tocontrol the engagement or disengagement of one or more VAR compensationcomponents of a switch-controlled VAR source as described herein.

FIG. 30 is a flowchart for isolating resonance utilizing the HMB 2900(see FIG. 29) within the switch-controlled VAR source 2600 (see FIG. 26)in some embodiments. Similar to FIG. 27, in step 3002, theswitch-controlled VAR source 2600 detects a first proximate voltage at apoint in the path (e.g., at a point in a power distribution network). Instep 3004, the switch-controlled VAR source 2600 compares the firstproximate voltage to a voltage threshold. In step 3006, theswitch-controlled VAR source 2600 determines to enable a VARcompensation component based on comparison to compensate for VAR inpath. This process may be analogous to other processes described herein(e.g., see FIG. 6).

In step 3008, the HMB 2900 detects a second proximate voltage. In oneexample, a voltage from transformer with windings 2904 and 2906 isreceived by the HMB 2900. The transformer may be coupled to the same ora similar position to the point in the path from which the firstproximate voltage was detected. In some embodiments, the capacitor 2908and inductor 2910 is an LC filter or otherwise assist in processing theoutput from the transformer.

In step 3010, the HMB 2900 detects if the second proximate voltage fromthe transformer is greater than a first and/or second resonancethreshold. In various embodiments, if the second proximate voltage issufficient to engage the switches. Those skilled in the art willappreciate that a processor may be configured to control the transistors2916 and 2918 via the lines 2920 and 2922 thereby allowing alteration ofthe first and/or second resonance compensation components.

In step 3012, the inverter of the HMB 2900 synthesizes harmonic voltagesin anti-phase to cancel the harmonic. For example, the inverter injectsharmonic voltages in anti-phase with the harmonic resonance so that theharmonic resonance is at least partially cancelled.

FIG. 31 is a diagram of an HMB 3100 that is configured to “detune”(e.g., shift) resonance through engagement or disengagement of one ormore capacitors and/or inductors of a switch-controlled VAR source (asdescribed herein) when voltage is greater than at least one resonancethreshold in some embodiments. In one example, once the processor 3122senses excessive harmonics, the processor 3122 may engage or disengageone or more VAR compensation components of a switch-controlled VARsource 2600 (see FIG. 26) to de-tune the harmonics. In variousembodiments, the processor 3122 may be the controller 2618.

The HMB 3100 comprises a line 3102, an inductor 3104, a diode bridge(i.e., diodes 3106, 3108, 3110, and 3112), LED 3114, and resistors 3116and 3118. An optical sensor 3120 coupled to the processor 3122 may beconfigured to receive light from the LED 3114. In some embodiments, theoptical sensor 3120 and/or the processor 3122 may be a part of the HMB3100.

In some embodiments, the HMB 3100 comprises a resonance detection moduleand a resonance compensation component. The resonance detection module,for example, may comprise, but not be limited to, the inductor 3104 andLED 3114 for comparing voltage to a resonance threshold. The resonancecompensation component may comprise, but not be limited to, thecapacitors and or inductors (e.g., the VAR compensation components) of aswitch-controlled VAR source.

As discussed with regard to FIG. 27, the inductor 3104, similar toinductor 2704) may serve to amply the higher frequency component becausethe voltage drop across the inductor 3104 may be approximated byV=w*L*i, where w is the harmonic frequency. As a result, the currentcomponent of the higher harmonic may have a larger voltage drop acrossthe inductor 3104. A relatively large amplitude harmonic current mayhave a large voltage drop causing the LED 3114 to emit light.

In various embodiments, the HMB 3100 receives voltage from line 3102across inductor 3104. The optional diode bridge (i.e., diodes 3106,3108, 3110, and 3112) may convert the voltage from AC to DC. Theresistors 3116 and 3118 may be an optional voltage divider. When the DCvoltage is sufficiently high, the LED 3114 emits light. In someembodiments, when the DC voltage is sufficiently high, the LED 3114emits light that, at a sufficient intensity, indicates that the voltageacross the inductor 3104 is potentially caused by resonance. Theprocessor 3122 may detect the light and, optionally, the intensity ofthe light, from the LED 3114 via the optical sensor 3120.

The processor 3122 may be configured to engage and/or disengage one ormore capacitors and/or inductors of a switch-controlled VAR source tode-tune the harmonics based on the indication from the LED 3114. Invarious embodiments, when LED 3114 emits light (e.g., any light or lightof sufficient intensity) based on received voltage, the voltage may besufficiently higher than a resonance threshold. The processor 3122 maydisengage the capacitor 2608 of switch-controlled VAR source 2600 (seeFIG. 26) based on an indication that the voltage is sufficiently high toconclude that the effects of resonance is potentially present.

Those skilled in the art will appreciate that the quality and propertiesof the components of the HMB 3100 may be chosen such that when thevoltage across the inductor 3104 is above a resonance threshold (i.e.,the point at which the LED 3114 emits light of sufficient intensity or,in another example, any light at all) or the divided, DC representationof the voltage across the inductor 3104 is above a resonance threshold,the processor may engage or disengage one or more capacitors and/orinductors of a switch-controlled VAR source. As a result resonance maybe altered, reduced, or eliminated.

The optical sensor 3120 may be further coupled to a voltage source(e.g., +5 volts) across one or more resistors as well as a path to othercircuitry or ground (See FIG. 31).

In various embodiments, the optical sensor 3120 and the processor 3122or electrically isolated from the LED 3114 and related components.

In various embodiments, the switch-controlled VAR source 2600 may beutilized to detect resonance through the initial voltage sensingconducted by the VAR source 2600 (e.g., utilizing the controller 2618.As a result, the HMB 3100 may not be required for the switch-controlledVAR source 2600 to detect resonance and engage/disengage one or moredifferent VAR compensation components to “de-tune” the resonance.

In various embodiments, any number of harmonic management devices (HMBs)may be utilized together. For example, a harmonic dampening block suchas HMB 2700 may dampen harmonics while harmonic isolation block such asHMB 2900 isolates remaining harmonics not sufficiently dampened by theharmonic dampening block. Further, a harmonic “de-tuning” block such asHMB 3100 may engage or disengage one or more VAR compensation componentsto shift or “de-tune” all or part of the remaining harmonics that werenot sufficiently dampened or isolated.

In another example, two or more of the same HMB devices may worktogether (e.g., a first HMB 2700 initially dampens harmonics and,subsequently, a second HMB 2700 further dampens harmonics remaining fromthe first HMB 2700). Those skilled in the art will appreciate that anynumber of HMBs of any kind may work together.

FIG. 32 is a flowchart for de-tuning resonance utilizing the HMB 3100(see FIG. 31) within the switch-controlled VAR source 2600 (see FIG. 26)in some embodiments. Similar to FIGS. 27 and 29, in step 3202, theswitch-controlled VAR source 2600 detects a first proximate voltage at apoint in the path (e.g., at a point in a power distribution network). Instep 3204, the switch-controlled VAR source 2600 compares the firstproximate voltage to a voltage threshold. In step 3206, theswitch-controlled VAR source 2600 determines to enable a VARcompensation component based on comparison to compensate for VAR inpath. This process may be analogous to other processes described herein(e.g., see FIG. 6).

In step 3208, the HMB 3100 detects a second proximate voltage. In oneexample, a voltage across inductor 3104 is received by the HMB 3100.Line 3102, coupled to inductor 3104, may be coupled to the same or asimilar position to the point in the path from which the first proximatevoltage was detected.

In optional step 3210, the HMB 3100 converts at least a portion of thesecond proximate voltage to DC utilizing the diode bridge (e.g., diodes3106, 3108, 3110, and 3112).

In step 3212, the HMB 2700 emits light from light source (e.g., LED3114) if second if the DC second proximate voltage is greater than aresonance threshold (e.g., the threshold for which the LED 3114 emitslight). In some embodiments, the DC proximate voltage is subject to avoltage divider (e.g., resistors 3116 and 3118). In some embodiments,the LED 3114 will emit light when the DC second proximate voltage isgreater than a resonance threshold.

In step 3214, the optical sensor 3120 detects light from the LED 3114and provides the information to a processor 3122. The processor 3122 maydetect the signal from the optical sensor 3120 and/or measure intensityto determine if the second proximate voltage is greater than theresonance threshold. In step 3216, a processor 3122 or other devicedisengages one or more VAR compensation components based on, at least inpart, the detected light from the LED 3114 to “de-tune” resonance.

In one example, the processor 3122 is the controller 2618 of theswitch-controlled VAR source 2600 (see FIG. 26). The controller 2618 mayreceive an indication that voltage across inductor 3104 is greater thanat least one resonance threshold and, subsequently the controller 2618may disengage the VAR compensation component (e.g., capacitor 2608) bycontrolling the relay 2610 and the semiconductor switch 2612.

In various embodiments, the switch-controlled VAR source may be a partof a pole top unit or other device with multiple VAR compensationcomponents (e.g., multiple capacitors and/or inductors). Based on theindication from the HMB 3100, the controller 2618 may disengage orengage any number of inductors and/or capacitors. Examples of this typeof architecture include, but are not limited to, depictions within FIGS.33 and 34 as well as descriptions related thereto.

FIG. 33 depicts a HMB 3308 in series with an inductive module 3310 and acapacitive module 3312 of one or more switch-controlled VAR sources insome embodiments. In circuit 3300, a power source 3304 of a powerdistribution network (e.g., a grid), provides power along line 3302 tothe load 3306. The HMB 3308 may be coupled to the line 3302, optionalinductive module 3310, and capacitive module 3312. The inductive module3310 may comprise inductor and semiconductor switch 3314 a-d. Thecapacitive module 3312 may comprise capacitor and semiconductor switch3316 a-d. There may be any number of inductors and semiconductorswitches. Similarly, there may be any number of capacitors andsemiconductor switches 3316 a-d.

In some embodiments, a switch-controlled VAR source may comprise theinductive module 3310 and the capacitive module 3312. In one example, acontroller may control each of the VAR compensation components of theinductive module 3310 and the capacitive module 3312 (e.g., thecontroller may control the inductor and semiconductor switch 3314 a-d aswell as the capacitor and semiconductor switch 3316 a-d). Theswitch-controlled VAR source may further comprise the HMB 3308.

The HMB 3308 may be any HMB. For example, the HMB 3308 may comprisecircuits as depicted with regard to FIGS. 27, 29, and 31. In oneexample, HMB 3308 comprises HMB 2700 (see FIG. 27). When voltage acrossinductor 2704 is greater than a threshold, the HMB 2700 may engage anynumber of resistors 2720 to dampen resonance that may be caused, forexample, by engaging inductors and/or capacitors of inductive module3310 and/or capacitive module 3312.

In another example, HMB 3308 comprises HMB 2900 (see FIG. 29). In thisexample, when voltage from a transformer is sufficient to overcome therelated resonance threshold(s) to isolate resonance by synthesizingharmonic voltages in anti-phase to cancel the harmonics.

In a further example, HMB 3308 comprises HMB 3100 (see FIG. 31). Whenvoltage across inductor 3104 is greater than a threshold, the LED 3114may emit light or light of sufficient intensity to the optical sensor3120. The processor 3122 may detect the light and determine that voltageacross the inductor 3104 may potentially indicating resonance.

In various embodiments, the processor (e.g., controller that controlsthe optional inductive module 3310 and the capacitive module 3312)controls one or more VAR compensation components of the inductive module3310 and the capacitive module 3312. For example, upon detectingpotential resonance, the processor may disengage two of ten engagedcapacitors of the capacitive module 3312. Subsequent detection ofvoltage may indicate that the resonance has been “de-tuned” (e.g.,shifted). If, upon subsequent detection of voltage that indicates thatresonance has not been sufficiently changed, the controller maydisengage more capacitors of the capacitive module 3312, disengageinductors of the inductive module 3310, and/or reengage any other VARcompensation components. The controller may be programmed to makechanges until the resonant condition is sufficiently changed.

Further, in various embodiments, the HMB 3308 may comprise any number ofHMBs (including the same or different HMBs).

In Although FIG. 33 depicts the HMB 3308 as being between the path 3302and the inductive module 3310 in parallel with the capacitive module3312, the HMB 3308 may be in any position. For example, the inductivemodule 3310 may be behind or in front of the HMB 3308.

The use of inductive and capacitive modules 3310 and 3312, and the useof harmonic isolation/dampening/shifting principles may provide a costeffective and highly efficient implementation of a fast and flexible VARsource. In various embodiments, such a system may be deployed in manyplaces without extensive studies to check for harmonic susceptibilityand may be scaled to the multi-MVAR level. The fast VAR source of FIGS.33 and 34, as well as alternatives than the embodiments depicted, mayfeature faster response than SVCs and may realize lower losses andunbalanced operation. Some embodiments may feature response comparableto STATCOMs and DVCs, but at lower cost and/or with the ability tooperate under severely unbalanced conditions.

FIG. 34 depicts a transformer 2406 coupled to an HMB 3410 and anoptional inductive module 3412, the HMB 3410 being further coupled tothe capacitive module 3414 in some embodiments. The HMB 3410 may becoupled to the line 3402, optional inductive module 3412, and capacitivemodule 3414. The inductive module 3412 may comprise inductor andsemiconductor switch 3416 a-d. The capacitive module 3414 may comprisecapacitor and semiconductor switch 3418 a-d. There may be any number ofinductors and semiconductor switches 3416 a-d. Similarly, there may beany number of capacitors and semiconductor switches 3418 a-d.

In some embodiments, as discussed with regard to FIG. 33, theswitch-controlled VAR source may comprise the inductive module 3412 andthe capacitive module 3414. In one example, a controller may controleach of the VAR compensation components of the inductive module 3412 andthe capacitive module 3414 (e.g., the controller may control theinductor and semiconductor switch 3416 a-d as well as the capacitor andsemiconductor switch 3418 a-d). The switch-controlled VAR source mayfurther comprise the HMB 3410.

The HMB 3410 may be any HMB or combination of HMBs. For example, the HMB3410 may comprise circuits as depicted with regard to FIGS. 27, 29, and31 and may function as described in FIG. 33.

Although FIG. 34 depicts the HMB 3410 as being between the inductivemodule 3412 and the capacitive module 3414, the HMB 3410 may be in anyposition. For example, the HMB 3410 may be between the transformer 3406and the modules (e.g., in front of the inductive module 3412 and thecapacitive module 3414).

As discussed herein, the fast VAR source comprising the HMB 3410, theinductive module 3412, and the capacitive module 3414 may be packaged ina compact enclosure, and can be connected to a transformer to match thelow voltage to the grid' medium voltage of around 4000 volts and higheras demonstrated in FIG. 34. The fast source could also be integratedinto a single enclosure with the grid interface transformer. This issimilar to other electrical equipment and is well known to one skilledin the art.

The above-described functions and components can be comprised ofinstructions that are stored on a storage medium such as a computerreadable medium. The instructions can be retrieved and executed by aprocessor. Some examples of instructions are software, program code, andfirmware. Some examples of storage medium are memory devices, tape,disks, integrated circuits, and servers. The instructions areoperational when executed by the processor to direct the processor tooperate in accord with embodiments of the present invention. Thoseskilled in the art are familiar with instructions, processor(s), andstorage medium.

Various embodiments are described herein as examples. It will beapparent to those skilled in the art that various modifications may bemade and other embodiments can be used without departing from thebroader scope of the present invention(s). Therefore, these and othervariations upon the exemplary embodiments are intended to be covered bythe present invention(s).

1. A system comprising: a distribution power network; a plurality ofloads at or near an edge of the distribution power network, each of theplurality of loads configured to receive power from the distributionpower network; a plurality of shunt-connected, switch-controlled VARsource at the edge or near the edge of the distribution power network,each of the plurality of shunt-connected, switch-controlled VAR sourcesconfigured to detect a first proximate voltage at the edge or near theedge of the distribution power network, each of the plurality ofshunt-connected, switch-controlled VAR sources comprising a firstprocessor and a voltage compensation component, the processor configuredto enable the shunt-connected, switch-controlled VAR source todetermine, after a delay, whether to enable the VAR compensationcomponent based on the first proximate voltage to adjust voltagevolt-ampere reactive by controlling the VAR compensation component basedon the determination; and a plurality of harmonic management blockscoupled to the distribution power network, each harmonic managementblock comprising a resonance detection module and a resonancecompensation component, each harmonic management block configured tocompare a second proximate voltage to at least one resonant threshold todetect potential resonance caused by enablement of the voltagecompensation component of at least one of the plurality ofshunt-connected, switch-controlled VAR sources, and to engage based onthe comparison the resonance compensation component to manage thepotential resonance.
 2. The system of claim 1, wherein the resonancedetection module comprises an inductor and a zener diode.
 3. The systemof claim 2, wherein the resonance threshold is the break down voltage ofthe zener diode.
 4. The system of claim 2, wherein the resonancecompensation component comprises a transistor and a resistor, thetransistor closing based on a comparison of voltage across the inductorto the resonance threshold to engage the resistor and dampen thepotential resonance.
 5. The system of claim 1, wherein the resonancedetection module comprises a transformer and an inverter.
 6. The systemof claim 5, wherein the resonance compensation component comprises atleast one capacitor and wherein the inverter with the at least onecapacitor is configured to synthesize harmonic voltages in anti-phase tocancel potential resonance.
 7. The system of claim 1, wherein theresonance detection module comprises an inductor and an LED.
 8. Thesystem of claim 7, wherein the resonance compensation componentcomprises a processor configured to enable or disable the VARcompensation component of at least one of the shunt-connected,switch-controlled VAR sources based on light from the LED.
 9. A systemcomprising: a distribution power network; a plurality of loads at ornear an edge of the distribution power network, each of the plurality ofloads configured to receive power from the distribution power network; aplurality of shunt-connected, switch-controlled VAR source at the edgeor near the edge of the distribution power network, each of theplurality of shunt-connected, switch-controlled VAR sources configuredto detect a first proximate voltage at the edge or near the edge of thedistribution power network, each of the plurality of shunt-connected,switch-controlled VAR sources comprising a first processor and a voltagecompensation component, the processor configured to enable theshunt-connected, switch-controlled VAR source to determine, after adelay, whether to enable the VAR compensation component based on thefirst proximate voltage to adjust voltage volt-ampere reactive bycontrolling the VAR compensation component based on the determination;and a plurality of means for managing potential resonance, the pluralityof means coupled to the distribution power network, each of theplurality of means comprising a resonance detection module and aresonance compensation component, each of the plurality of meansconfigured to compare a second proximate voltage to at least oneresonant threshold to detect potential resonance caused by enablement ofthe voltage compensation component of at least one of the plurality ofshunt-connected, switch-controlled VAR sources, and to engage based onthe comparison the resonance compensation component to manage thepotential resonance.
 10. A system comprising: a first switch-controlledVAR source configured to be coupled to a distribution power network, thefirst switch-controlled VAR source comprising a first processor, avoltage compensation component, and a switch, the first processorconfigured to enable the voltage compensation component after a delay bycontrolling the switch based on first proximate voltage after a durationassociated with the delay to adjust voltage volt-ampere reactive; and aharmonic management block configured to be coupled to the distributionpower network, the harmonic management block comprising a resonancedetection module and a resonance compensation component, the harmonicmanagement block configured to compare a second proximate voltage to atleast one resonant threshold to detect potential resonance caused byenablement of the voltage compensation component and to engage based onthe comparison the resonance compensation component to manage thepotential resonance.
 11. The system of claim 10, wherein the resonancedetection module comprises an inductor and a zener diode.
 12. The systemof claim 11, wherein the resonance threshold is the break down voltageof the zener diode.
 13. The system of claim 11, wherein the resonancecompensation component comprises a transistor and a resistor, thetransistor closing based on a comparison of voltage across the inductorto the resonance threshold to engage the resistor and dampen thepotential resonance.
 14. The system of claim 10, wherein the resonancedetection module comprises a transformer and an inverter.
 15. The systemof claim 14, wherein the resonance compensation component comprises atleast one capacitor and wherein the inverter with the at least onecapacitor is configured to synthesize harmonic voltages in anti-phase tocancel potential resonance.
 16. The system of claim 10, wherein theresonance detection module comprises an inductor and an LED.
 17. Thesystem of claim 16, wherein the resonance compensation componentcomprises a processor configured to enable or disable the VARcompensation component of at least one of the shunt-connected,switch-controlled VAR sources based on light from the LED.
 18. A systemcomprising: a first switch-controlled VAR source configured to becoupled to a distribution power network, the first switch-controlled VARsource comprising a first processor, a voltage compensation component,and a switch, the first processor configured to enable the voltagecompensation component after a delay by controlling the switch based onfirst proximate voltage after a duration associated with the delay toadjust voltage volt-ampere reactive; and a harmonic management blockconfigured to be coupled to the distribution power network, the harmonicmanagement block comprising a means for detecting resonance and a meansfor compensation of resonance, the means for detecting resonanceconfigured to compare a second proximate voltage to at least oneresonant threshold to detect potential resonance caused by enablement ofthe voltage compensation component and the means for compensation ofresonance configured to manage the potential resonance based on thecomparison.
 19. A method comprising: installing a firstswitch-controlled VAR source configured to a distribution power network,the first switch-controlled VAR source comprising a first processor, avoltage compensation component, and a switch, the first processorconfigured to enable the voltage compensation component after a delay bycontrolling the switch based on first proximate voltage after a durationassociated with the delay to adjust voltage volt-ampere reactive; andinstalling a harmonic management block configured to the distributionpower network, the harmonic management block comprising a resonancedetection module and a resonance compensation component, the harmonicmanagement block configured to compare a second proximate voltage to atleast one resonant threshold to detect potential resonance caused byenablement of the voltage compensation component and to engage based onthe comparison the resonance compensation component to manage thepotential resonance.